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 A177399 O.g.f.: exp( Sum_{n>=1} (sigma(2n)-sigma(n))^n * x^n/n ). 3
 1, 2, 10, 188, 1414, 53596, 2923652, 44668152, 651967302, 605335444140, 7564881098284, 157357140966472, 96537385644719004, 695895399853879448, 86358988630956719304, 1103071610291574716763120 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Here sigma(n) = A000203(n) is the sum of divisors of n. Compare g.f. to the formula for Jacobi theta_4(x) given by: . theta_4(x) = exp( Sum_{n>=1} -(sigma(2n)-sigma(n))*x^n/n ) where theta_4(x) = 1 + Sum_{n>=1} 2*(-x)^(n^2). LINKS Table of n, a(n) for n=0..15. EXAMPLE G.f.: A(x) = 1 + 2*x + 10*x^2 + 188*x^3 + 1414*x^4 + 53596*x^5 +... log(A(x)) = 2*x + 4^2*x^2/2 + 8^3*x^3/3 + 8^4*x^4/4 + 12^5*x^5/5 +...+ A054785(n)^n*x^n/n +... PROG (PARI) {a(n)=polcoeff(exp(sum(m=1, n, (sigma(2*m)-sigma(m))^m*x^m/m)+x*O(x^n)), n)} CROSSREFS Cf. A054785, A000203, A177398, A155200. Sequence in context: A057119 A226563 A037267 * A194971 A155200 A264563 Adjacent sequences: A177396 A177397 A177398 * A177400 A177401 A177402 KEYWORD nonn AUTHOR Paul D. Hanna, May 30 2010 STATUS approved

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Last modified June 13 07:46 EDT 2024. Contains 373366 sequences. (Running on oeis4.)