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 A181893 Number of different nonnegative solutions of equation: x^2 - y^2 = k! for 1 <= k <= n. 1

%I

%S 1,1,1,3,7,16,34,70,130,235,445,769,1417,2497,4177,6529,11233,17713,

%T 30673,49033,76233,119433,205833,316713,471945,715881,1026345,1449705,

%U 2296425,3376425,5536425,8128425,11814825,17528745,25242537,34480425,52956201,81509673

%N Number of different nonnegative solutions of equation: x^2 - y^2 = k! for 1 <= k <= n.

%F a(n)=sum(k=1..n, A138196(k) )

%t kkk = 1; cc = {1, 1, 1}; Do[w = n!/4; kk = Floor[(DivisorSigma[0, w] + 1)/2]; kkk = kkk + kk; AppendTo[cc, kkk], {n, 4, 54}]; cc

%Y Cf. A138196, A139151, A181892.

%K nonn

%O 1,4

%A _Artur Jasinski_, Mar 31 2012

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Last modified October 20 10:45 EDT 2019. Contains 328257 sequences. (Running on oeis4.)