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A053781
Numbers k that divide the sum of the first k composite numbers.
4
1, 2, 3, 7, 11, 71, 107, 115, 139, 155, 681, 1671, 4876, 21464, 30046, 311271, 788749, 10893662, 20743270, 134568163, 163879554, 920161004, 6364787032, 21400458779, 47934932406, 56133884369, 288050185452, 536023681676, 1484061538595
OFFSET
1,2
FORMULA
Numbers k such that k divides A053767(k). - Robert G. Wilson v, Nov 24 2004
MATHEMATICA
c = s = 0; Do[ If[ !PrimeQ[n], c++; s = s + n; If[ Mod[s, c] == 0, Print[c]]], {n, 2, 10^9}] (* Robert G. Wilson v, Nov 23 2004 *)
PROG
(PARI) lista(nn) = {s = 0; n = 0; forcomposite(c=0, nn, s += c; n++; if (! (s % n), print1(n, ", ")); ); } \\ Michel Marcus, Mar 15 2015
CROSSREFS
KEYWORD
nonn
AUTHOR
G. L. Honaker, Jr., Mar 29 2000
EXTENSIONS
a(19)-a(22) from Robert G. Wilson v, Nov 24 2004
a(23)-a(26) from Sean A. Irvine, Oct 01 2009
a(27)-a(29) from Donovan Johnson, Jul 06 2010
STATUS
approved