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%I #42 May 25 2022 02:53:45
%S 4,13,35,52,95,119,169,676,11596,57577,159484,276773,360139,1345747,
%T 56193997,60640957,604170268,807129973
%N Numbers k that divide s(k-1), where s(1) = 1, s(k) = s(k-1) + (k+1)*3^k.
%C No other terms below 300000. - _Vaclav Kotesovec_, May 05 2018
%C {s(n)} = {1, 28, 136, 541, 1999, 7102, 24598, ...}; 4*s(n) = 3^(n+1)*(2n+1) - 23, with g.f. x*(-1-21*x+45*x^2) / ( (x-1)*(-1+3*x)^2 ). - _R. J. Mathar_, May 05 2018
%t seq = RecurrenceTable[{s[n] == s[n - 1] + (n + 1)*3^n, s[1] == 1}, s, {n, 1, 20000}]; Select[Range[1, Length[seq]], Divisible[seq[[# - 1]], #] &] (* _Vaclav Kotesovec_, May 05 2018 *)
%K nonn,more
%O 1,1
%A _Robert G. Wilson v_, Sep 13 2000
%E Minor edits by _Altug Alkan_, May 05 2018
%E a(10)-a(12) from _Vaclav Kotesovec_, May 05 2018
%E a(13)-a(14) from _Chai Wah Wu_, Aug 26 2021
%E a(15)-a(16) from _Chai Wah Wu_, Sep 02 2021
%E a(17)-a(18) from _Sean A. Irvine_, May 25 2022
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