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 A181893 Number of different nonnegative solutions of equation: x^2 - y^2 = k! for 1 <= k <= n. 1
 1, 1, 1, 3, 7, 16, 34, 70, 130, 235, 445, 769, 1417, 2497, 4177, 6529, 11233, 17713, 30673, 49033, 76233, 119433, 205833, 316713, 471945, 715881, 1026345, 1449705, 2296425, 3376425, 5536425, 8128425, 11814825, 17528745, 25242537, 34480425, 52956201, 81509673 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,4 LINKS FORMULA a(n)=sum(k=1..n, A138196(k) ) MATHEMATICA 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 CROSSREFS Cf. A138196, A139151, A181892. Sequence in context: A002936 A014668 A182615 * A054455 A178455 A281811 Adjacent sequences:  A181890 A181891 A181892 * A181894 A181895 A181896 KEYWORD nonn AUTHOR Artur Jasinski, Mar 31 2012 STATUS approved

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Last modified September 17 22:53 EDT 2019. Contains 327147 sequences. (Running on oeis4.)