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A196457 E.g.f.: A(x) = Sum_{n>=0} exp((2^n + (-1)^n)*x) * (2^n + (-1)^n)^n * x^n/n!. 3
1, 3, 31, 729, 96895, 35927793, 81108563671, 567783612614529, 19581520178825073535, 2420011073132910603900513, 1292280969200128366004695992151, 2658679109878459106807828064662797809, 22431208469091982323298987880694649428158815, 748294346623782293365235855701111498805828889778353 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

GENERAL BINOMIAL IDENTITY.

When p=-1, q=2, this sequence illustrates the following identity.

Given e.g.f.: Sum_{n>=0} (p^n+q^n)^n*exp((p^n+q^n)*x)*x^n/n! = Sum_{n>=0} a(n)*x^n/n!,

then a(n) = Sum_{k=0..n} C(n,k)*(p^k + q^k)^n =  Sum_{k=0..n} C(n,k)*(1 + p^(n-k)*q^k)^n;

which is a special case of the more general binomial identity:

Sum_{k=0..n} C(n,k)*(s*p^k + t*q^k)^(n-k) * (u*p^k + v*q^k)^k = Sum_{k=0..n} C(n,k)*(s + u*p^(n-k)*q^k)^(n-k) * (t + v*p^(n-k)*q^k)^k.

LINKS

Table of n, a(n) for n=0..13.

FORMULA

GENERATING FUNCTIONS.

E.g.f.: Sum_{n>=0} (2^n + (-1)^n)^n * exp( (2^n + (-1)^n)*x ) * x^n/n!.

O.g.f.: Sum_{n>=0} (2^n + (-1)^n)^n * x^n / (1 - (2^n + (-1)^n)*x)^(n+1). - Paul D. Hanna, Jul 13 2019

FORMULAS FOR TERMS.

a(n) = Sum_{k=0..n} C(n,k)*(2^k + (-1)^k)^n.

EXAMPLE

E.g.f.: A(x) = 1 + 3*x + 31*x^2/2! + 729*x^3/3! + 96895*x^4/4! +...

where

A(x) = exp((1+1)*x) + (2-1)*exp((2-1)*x)*x + (2^2+1)^2*exp((2^2+1)*x)*x^2/2! + (2^3-1)^3*exp((2^3-1)*x)*x^3/3! +...

or, equivalently,

A(x) = exp(2*x) + 1*exp(1*x)*x + 5^2*exp(5*x)*x^2/2! + 7^3*exp(7*x)*x^3/3! + 17^4*exp(17*x)*x^4/4! + 31^5*exp(31*x)*x^5/5! +...

Illustrate the formula for the terms:

a(1) = (1+1) + (2-1) = 3 ;

a(2) = (1+1)^2 + 2*(2-1)^2 + (2^2+1)^2 = 2^2 + 2*1^2 + 5^2 = 31 ;

a(3) = (1+1)^3 + 3*(2-1)^3 + 3*(2^2+1)^3 + (2^3-1)^3 = 2^3 + 3*1^3 + 3*5^3 + 7^3 = 729 ;

a(4) = (1+1)^4 + 4*(2-1)^4 + 6*(2^2+1)^4 + 4*(2^3-1)^4 + (2^4+1)^4 = 2^4 + 4*1^4 + 6*5^4 + 4*7^4 + 17^4 = 96895.

PROG

(PARI) {a(n)=n!*polcoeff(sum(m=0, n, exp((2^m+(-1)^m+x*O(x^n))*x)*(2^m+(-1)^m)^m*x^m/m!), n)}

(PARI) {a(n)=sum(k=0, n, binomial(n, k)*(2^k + (-1)^k)^n)}

(PARI) {a(n)=local(p=-1, q=2); n!*polcoeff(sum(m=0, n, (p^m+q^m)^m*exp((p^m+q^m+x*O(x^n))*x)*x^m/m!), n)}

(PARI) {a(n)=local(p=-1, q=2, s=1, t=1, u=1, v=1);

sum(k=0, n, binomial(n, k)*(s*p^k + t*q^k)^(n-k)*(u*p^k + v*q^k)^k)}

(PARI) /* right side of the general binomial identity: */

{a(n)=local(p=-1, q=2, s=1, t=1, u=1, v=1);

sum(k=0, n, binomial(n, k)*(s + u*p^(n-k)*q^k)^(n-k) * (t + v*p^(n-k)*q^k)^k)}

CROSSREFS

Cf. A138247, A196458, A196459, A196460.

Sequence in context: A092552 A322487 A300735 * A136370 A317348 A144416

Adjacent sequences:  A196454 A196455 A196456 * A196458 A196459 A196460

KEYWORD

nonn

AUTHOR

Paul D. Hanna, Oct 03 2011

STATUS

approved

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Last modified September 20 20:12 EDT 2019. Contains 327247 sequences. (Running on oeis4.)