The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A119730 (Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
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A119730

Primes p such that p+1, p+2, p+3, p+4 and p+5 have equal number of divisors.
(history; published version)

#13 by Andrew Howroyd at Sun Jan 26 11:03:12 EST 2020

STATUS

reviewed

approved

#12 by Joerg Arndt at Sun Jan 26 10:49:23 EST 2020

STATUS

proposed

reviewed

#11 by Amiram Eldar at Sun Jan 26 10:41:21 EST 2020

STATUS

editing

proposed

#10 by Amiram Eldar at Sun Jan 26 10:38:01 EST 2020

EXAMPLE

13781 is OK a term since 13782, 13783, 13784, 13785 and 13786 all have 8 divisors:

#9 by Amiram Eldar at Sun Jan 26 10:37:42 EST 2020

CROSSREFS

Cf. A008329, A049234, A119705, A119711, A119728, A119740.

#8 by Amiram Eldar at Sun Jan 26 10:37:11 EST 2020

LINKS

Amiram Eldar, <a href="/A119730/b119730.txt">Table of n, a(n) for n = 1..10000</a>

STATUS

approved

editing

#7 by Harvey P. Dale at Wed Jan 16 17:34:51 EST 2019

STATUS

editing

approved

#6 by Harvey P. Dale at Wed Jan 16 17:34:49 EST 2019

MATHEMATICA

endQ[n_]:= Length[Union[DivisorSigma[0, #]&/@ (n + Range[5])]]]==1; Select[Prime[ Range[ 200000]], endQ] (* Harvey P. Dale, Jan 16 2019 *)

STATUS

approved

editing

#5 by Harvey P. Dale at Wed Jan 16 17:32:53 EST 2019

STATUS

editing

approved

#4 by Harvey P. Dale at Wed Jan 16 17:32:49 EST 2019

MATHEMATICA

endQ[n_]:=Length[Union[DivisorSigma[0, #]&/@(n+Range[5])]]==1; Select[Prime[ Range[ 200000]], endQ] (* Harvey P. Dale, Jan 16 2019 *)

STATUS

approved

editing