A159309
L.g.f.: Sum_{n>=1} a(n)*x^n/n = Sum_{n>=1} (1 + sigma(n)*x)^n * x^n/n.
Original entry on oeis.org
1, 3, 10, 35, 116, 606, 2990, 11203, 65368, 567558, 3229942, 12730946, 78628616, 666394746, 3968286590, 21143707843, 160244432497, 1602468019110, 20852615681805, 320475672814590, 4102188681702086, 36438823274699332
Offset: 1
L.g.f.: L(x) = x + 3*x^2/2 + 10*x^3/3 + 35*x^4/4 + 116*x^5/5 +...
L(x) = (1+x)*x + (1+3*x)^2*x^2/2 + (1+4*x)^3*x^3/3 + (1+7*x)^4*x^4/4 +...
exp(L(x)) = 1 + x + 2*x^2 + 5*x^3 + 14*x^4 + 40*x^5 + 154*x^6 +... (A159308).
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{a(n)=n*polcoeff(sum(m=1,n+1,(1+sigma(m)*x+x*O(x^n))^m*x^m/m),n)}
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{a(n)=n*sum(k=0,n\2,binomial(n-k,k)*sigma(n-k)^k/(n-k))}
A163189
G.f.: A(x) = exp( Sum_{n>=1} (1 + A000204(n)*x)^n * x^n/n ).
Original entry on oeis.org
1, 1, 2, 5, 14, 40, 159, 812, 5133, 42942, 474619, 6708142, 121367878, 2819170132, 83571532538, 3148951107867, 151069353323782, 9219463980803329, 714951048370178409, 70448496563603216429, 8818161368662624534857
Offset: 0
G.f.: A(x) = 1 + x + 2*x^2 + 5*x^3 + 14*x^4 + 40*x^5 + 159*x^6 +...
A163572
G.f.: A(x) = exp( Sum_{n>=1} (1 + 2*A006519(n)*x)^n * x^n/n ) where A006519(n) is the highest power of 2 dividing n.
Original entry on oeis.org
1, 1, 3, 7, 19, 39, 169, 765, 2183, 4131, 11561, 55157, 666381, 8175433, 68536455, 355280675, 1048740623, 1931107235, 5055100985, 13108206741, 38734589993, 143320957605, 1022112572635, 26523801989399, 914332703582521
Offset: 0
G.f.: A(x) = 1 + x + 3*x^2 + 7*x^3 + 19*x^4 + 39*x^5 + 169*x^6 +...
log(A(x)) = (1+2*x)*x + (1+4*x)^2*x^2/2 + (1+2*x)^3*x^3/3 + (1+8*x)^4*x^4/4 +...
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{a(n)=polcoeff(exp(sum(m=1, n+1, (1+2^valuation(2*m,2)*x+x*O(x^n))^m*x^m/m)), n)}
Showing 1-3 of 3 results.
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