The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A278913 (Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
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A278913

a(n) is the smallest number k with prime sum of divisors such that tau(k) = n-th prime.
(history; published version)

#25 by Charles R Greathouse IV at Thu Sep 08 08:46:18 EDT 2022

PROG

(MAGMAMagma) A278913:=func<n|exists(r){k:k in[1..10000000] | IsPrime(SumOfDivisors(k)) and NumberOfDivisors(k) eq NthPrime(n)} select r else 0>; [A278913(n): n in[1..8]]

Discussion

Thu Sep 08

08:46

OEIS Server: https://oeis.org/edit/global/2944

#24 by Bruno Berselli at Thu Dec 29 03:55:40 EST 2016

STATUS

reviewed

approved

#23 by Joerg Arndt at Thu Dec 29 03:26:17 EST 2016

STATUS

proposed

reviewed

#22 by Michel Marcus at Wed Dec 28 16:34:22 EST 2016

STATUS

editing

proposed

#21 by Michel Marcus at Wed Dec 28 16:34:18 EST 2016

NAME

a(n) = is the smallest number k with prime sum of divisors such that tau(k) = n-th prime.

STATUS

proposed

editing

#20 by Davin Park at Wed Dec 28 16:25:19 EST 2016

STATUS

editing

proposed

#19 by Davin Park at Wed Dec 28 16:25:12 EST 2016

MATHEMATICA

A278913[n_] := BlockNestWhile[{x = NextPrime, 2}, While[, ! PrimeQ[Cyclotomic[Prime[n], x]#], x = NextPrime[x] &]; x^(Prime[n] - 1)] (* Davin Park, Dec 08 28 2016 *)

STATUS

approved

editing

#18 by Joerg Arndt at Sat Dec 10 11:23:06 EST 2016

STATUS

reviewed

approved

#17 by Michel Marcus at Sat Dec 10 11:12:42 EST 2016

STATUS

proposed

reviewed

#16 by Davin Park at Sat Dec 10 10:57:56 EST 2016

STATUS

editing

proposed

Discussion

Sat Dec 10

11:12

Michel Marcus: Yes Davin, you're right. Thanks for spotting my mistake.