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 A326272 E.g.f.: Sum_{n>=0} ((1+x)^n - 1)^n * 2^n / n!. 4
 1, 2, 16, 264, 6736, 240160, 11214144, 657138944, 46862522368, 3973718103552, 393443889049600, 44826129808396288, 5806491899779117056, 846541984240702889984, 137723354275132587802624, 24818755539270666795663360, 4922319631768240931906584576, 1068365636390386171090826297344, 252495346180630403940163162472448, 64688594470052384103192832427687936, 17893635413553390198442202310639616000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS More generally, the following sums are equal: (1) Sum_{n>=0} (q^n + p)^n * r^n/n!, (2) Sum_{n>=0} q^(n^2) * exp(p*q^n*r) * r^n/n!; here, q = (1+x) and p = -1, r = 2. In general, let F(x) be a formal power series in x such that F(0)=1, then Sum_{n>=0} m^n * F(q^n*r)^p * log( F(q^n*r) )^n / n! = Sum_{n>=0} r^n * [y^n] F(y)^(m*q^n + p); here, F(x) = exp(x), q = 1+x, p = -1, r = 2, m = 1. LINKS Paul D. Hanna, Table of n, a(n) for n = 0..300 FORMULA E.g.f. may be expressed by the following sums. (1) Sum_{n>=0} ((1+x)^n - 1)^n * 2^n / n!. (2) Sum_{n>=0} (1+x)^(n^2) * exp(-2*(1+x)^n) * 2^n / n!. EXAMPLE E.g.f: A(x) = 1 + 2*x + 16*x^2/2! + 264*x^3/3! + 6736*x^4/4! + 240160*x^5/5! + 11214144*x^6/6! + 657138944*x^7/7! + 46862522368*x^8/8! + 3973718103552*x^9/9! + 393443889049600*x^10/10! +... such that A(x) = 1 + 2*((1+x) - 1) + 2^2*((1+x)^2 - 1)^2/2! + 2^3*((1+x)^3 - 1)^3/3! + 2^4*((1+x)^4 - 1)^4/4! + 2^5*((1+x)^5 - 1)^5/5! + 2^6*((1+x)^6 - 1)^6/6! + 2^7*((1+x)^7 - 1)^7/7! + ... also A(x) = 1 + 2*(1+x)*exp(-2*(1+x)) + 2^2*(1+x)^4*exp(-2*(1+x)^2)/2! + 2^3*(1+x)^9*exp(-2*(1+x)^3)/3! + 2^4*(1+x)^16*exp(-2*(1+x)^4)/4! + 2^5*(1+x)^25*exp(-2*(1+x)^5)/5! + 2^6*(1+x)^36*exp(-2*(1+x)^6)/6! + 2^7*(1+x)^49*exp(-2*(1+x)^7)/7! + ... PROG (PARI) {a(n)=n!*polcoeff(sum(m=0, n, 2^m*((1+x+x*O(x^n))^m-1)^m/m!), n)} for(n=0, 30, print1(a(n), ", ")) CROSSREFS Cf. A192935, A326273, A326274. Cf. A326092. Sequence in context: A090305 A246739 A304317 * A283685 A197458 A050974 Adjacent sequences:  A326269 A326270 A326271 * A326273 A326274 A326275 KEYWORD nonn AUTHOR Paul D. Hanna, Jun 22 2019 STATUS approved

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Last modified January 25 16:42 EST 2020. Contains 331245 sequences. (Running on oeis4.)