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 A227733 a(n) = sigma(2*n)^2 - sigma(n)^2. 2
 8, 40, 128, 176, 288, 640, 512, 736, 1352, 1440, 1152, 2816, 1568, 2560, 4608, 3008, 2592, 6760, 3200, 6336, 8192, 5760, 4608, 11776, 7688, 7840, 12800, 11264, 7200, 23040, 8192, 12160, 18432, 12960, 18432, 29744, 11552, 16000, 25088, 26496, 14112, 40960, 15488, 25344, 48672, 23040 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Here sigma(n) is the sum of divisors of n (A000203). LINKS Paul D. Hanna, Table of n, a(n) for n = 1..1000 FORMULA Logarithmic derivative of A227732. EXAMPLE L.g.f.: L(x) = 8*x + 40*x^2/2 + 128*x^3/3 + 176*x^4/4 + 288*x^5/5 + 640*x^6/6 +... where exp(L(x)) = 1 + 8*x + 52*x^2 + 288*x^3 + 1396*x^4 + 6208*x^5 + 25744*x^6 +...+ A227732(n)*x^n +... PROG (PARI) {a(n)=sigma(2*n)^2-sigma(n)^2} for(n=1, 50, print1(a(n), ", ")) CROSSREFS Cf. A227732. Sequence in context: A135796 A105374 A162668 * A191903 A028596 A264602 Adjacent sequences: A227730 A227731 A227732 * A227734 A227735 A227736 KEYWORD nonn AUTHOR Paul D. Hanna, Jul 24 2013 STATUS approved

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Last modified December 6 06:06 EST 2022. Contains 358595 sequences. (Running on oeis4.)