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A142337 Numbers n such that sum(i=1..n, sigma(i)) is prime. 0
7, 12, 18, 23, 24, 32, 49, 66, 84, 87, 90, 92, 111, 112, 113, 114, 129, 130, 132, 133, 137, 138, 199, 238, 239, 271, 275, 278, 283, 285, 307, 313, 314, 317, 319, 322, 340, 342, 352, 357, 392, 394, 397, 399, 442, 443, 491, 492, 494, 499, 500, 505, 507, 508, 541, 545, 551, 552, 573, 574, 589, 590, 597, 598, 599, 600, 610, 619, 622, 648, 649, 650 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Numbers n such that A024916(n) is prime.

LINKS

Table of n, a(n) for n=1..72.

MATHEMATICA

Flatten[Table[If[PrimeQ[Sum[DivisorSigma[1, i], {i, 1, n}]], n, {}], {n, 1, 300}]].

Position[Accumulate[DivisorSigma[1, Range[650]]], _?PrimeQ]//Flatten (* Harvey P. Dale, Oct 12 2020 *)

PROG

(PARI) t=0; for(n=1, 1e3, if(isprime(t+=sigma(n)), print1(n", "))) \\ Charles R Greathouse IV, Nov 07 2011

CROSSREFS

Cf. A024916.

Sequence in context: A272808 A092094 A064665 * A131912 A247159 A022953

Adjacent sequences:  A142334 A142335 A142336 * A142338 A142339 A142340

KEYWORD

nonn

AUTHOR

Roger L. Bagula and Gary W. Adamson, Sep 18 2008

EXTENSIONS

Corrected and extended by Harvey P. Dale, Oct 12 2020

STATUS

approved

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Last modified May 22 15:29 EDT 2022. Contains 353957 sequences. (Running on oeis4.)