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A063731 Numbers k such that Sum_{j=1..k} sigma(j) divides Product_{j=1..k} sigma(j). 1
1, 5, 8, 15, 50, 52, 53, 55, 63, 68, 72, 96, 103, 157, 176, 196, 211, 219, 287, 288, 302, 303, 321, 327, 348, 360, 364, 365, 381, 402, 417, 421, 430, 431, 438, 444, 452, 454, 465, 472, 478, 504, 506, 512, 514, 530, 531, 534, 555, 565, 576, 584, 588, 594, 607 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Harry J. Smith, Table of n, a(n) for n = 1..1000

PROG

(PARI) for(n=1, 300, a=sum(k=1, n, sigma(k)); b=prod(k=1, n, sigma(k)); if(Mod(b, a)==0, print(n)))

(PARI) { n=0; a=0; b=1; for (m=1, 10^9, a+=sigma(m); b*=sigma(m); if (b%a==0, write("b063731.txt", n++, " ", m); if (n==1000, break)) ) } \\ Harry J. Smith, Aug 28 2009

CROSSREFS

Sequence in context: A259724 A259585 A220034 * A129316 A039752 A141536

Adjacent sequences:  A063728 A063729 A063730 * A063732 A063733 A063734

KEYWORD

easy,nonn

AUTHOR

Jason Earls, Aug 12 2001

EXTENSIONS

More terms from Matthew Conroy, Aug 21 2001

STATUS

approved

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Last modified November 20 15:02 EST 2018. Contains 317402 sequences. (Running on oeis4.)