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A135867 G.f. satisfies A(x) = 1 + x*A(2*x)^2. 11
1, 1, 4, 36, 640, 21888, 1451008, 188941312, 48768745472, 25069815595008, 25722272102744064, 52730972085034156032, 216091838647321476726784, 1770657164881170759078117376, 29013990909330956353981535748096 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,3
COMMENTS
Self-convolution equals A135868 such that 2^n*A135868(n) = a(n+1) for n >= 0.
LINKS
FORMULA
a(n) = 2^(n-1)*Sum_{k=0..n-1} a(k)*a(n-k-1) for n>0 with a(0)=1. - Paul D. Hanna, Feb 09 2010
a(n) ~ c * 2^(n*(n+1)/2), where c = 0.715337433614869740944075474484711589980951273610257702786245519231799678... - Vaclav Kotesovec, Nov 04 2021
MATHEMATICA
nmax = 15; A[_] = 0; Do[A[x_] = 1 + x*A[2*x]^2 + O[x]^(nmax + 1) // Normal, nmax + 1]; CoefficientList[A[x], x] (* Vaclav Kotesovec, Nov 04 2021 *)
PROG
(PARI) {a(n)=local(A=1+x+x*O(x^n)); for(i=0, n, A=1+x*subst(A, x, 2*x)^2); polcoeff(A, n)}
(PARI) a(n)=if(n==0, 1, 2^(n-1)*sum(k=0, n-1, a(k)*a(n-k-1))) \\ Paul D. Hanna, Feb 09 2010
CROSSREFS
Sequence in context: A241029 A002761 A002084 * A268470 A365650 A214347
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Dec 02 2007
STATUS
approved

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Last modified May 24 04:41 EDT 2024. Contains 372772 sequences. (Running on oeis4.)