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 A159555 Numbers n where n^2 divides A159553(n), where A159553(n) = Sum_{k=0..n} binomial(n,k) * gcd(n,k). 0

%I

%S 1,6,22,72,114,148,164,260,261,780,1078,1184,1266,2952,4674

%N Numbers n where n^2 divides A159553(n), where A159553(n) = Sum_{k=0..n} binomial(n,k) * gcd(n,k).

%C For the purpose of this sequence, gcd(n,0) = n.

%p A159068 := proc(n) option remember; add(binomial(n, k)*gcd(k, n), k=1..n) ; end: A159553 := proc(n) option remember ; A159068(n)+n; end: isA159555 := proc(n) if A159553(n) mod ( n^2) = 0 then true; else false; fi; end: for n from 1 do if isA159555(n) then printf("%d,\n",n) ; fi; od: # _R. J. Mathar_, Apr 29 2009

%Y Cf. A159553, A159554, A159458.

%K nonn

%O 1,2

%A _Leroy Quet_, Apr 15 2009

%E Extended by _R. J. Mathar_, Apr 29 2009

%E a(14)-a(15) from _Ray Chandler_, Jun 18 2009

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Last modified June 25 18:36 EDT 2019. Contains 324353 sequences. (Running on oeis4.)