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#22 by Amiram Eldar at Fri Jun 05 12:47:44 EDT 2020
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#21 by Amiram Eldar at Fri Jun 05 12:47:41 EDT 2020
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| FORMULA
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Numbers n such that both n and n+1 are of the form p^3 * q * r * s * ... where p, q, r, ... are distinct primes (with zereozero or more primes q, r, s, ...). - Charles R Greathouse IV, Jun 05 2020
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| STATUS
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approved
editing
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#20 by Charles R Greathouse IV at Fri Jun 05 10:42:45 EDT 2020
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#19 by Charles R Greathouse IV at Fri Jun 05 10:42:29 EDT 2020
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| FORMULA
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Numbers n such that both n and n+1 are of the form p^3 * q * r * s * ... where p, q, r, ... are distinct primes (with zereo or more primes q, r, s, ...). - Charles R Greathouse IV, Jun 05 2020
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| CROSSREFS
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Subsequence of A048109 and A000037.
Cf. A000005, A034444, A048105, A048109.
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| STATUS
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approved
editing
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#18 by Alois P. Heinz at Thu Jun 04 15:21:41 EDT 2020
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#17 by Michel Marcus at Thu Jun 04 12:11:42 EDT 2020
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#16 by Michel Marcus at Thu Jun 04 12:11:13 EDT 2020
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| MATHEMATICA
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seqQ[n_] := DivisorSigma[0, n] == 2^(PrimeNu[n] + 1); q1 = seqQ[1]; s = {}; Do[q2 = seqQ[n]; If[q1 && q2, AppendTo[s, n-1]]; q1 = q2, {n, 2, 10^4}]; s (* typo corrected by _Zak Seidov_, Jun 04 2020 *)
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| STATUS
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proposed
editing
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Discussion
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| Thu Jun 04
| 12:11
| Michel Marcus: so removed
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#15 by Amiram Eldar at Thu Jun 04 11:53:44 EDT 2020
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#14 by Amiram Eldar at Thu Jun 04 11:52:09 EDT 2020
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| MATHEMATICA
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seqQ[n_] := DivisorSigma[0, n] == 2^(PrimeNu[n] + 1); q1 = QseqQ[1]; s = {}; Do[q2 = seqQ[n]; If[q1 && q2, AppendTo[s, n-1]]; q1 = q2, {n, 2, 10^4}]; s (* typo corrected by Zak Seidov, Jun 04 2020 *)
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proposed
editing
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Discussion
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| Thu Jun 04
| 11:53
| Amiram Eldar: I have fixed it (it run properly also with this typo - this is why I didn't spot it in the run). Thanks.
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#13 by Michel Marcus at Thu Jun 04 10:49:57 EDT 2020
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