A324308 G.f.: Sum_{n>=0} (2^n + i)^n * x^n / (1 + 2^n*i*x)^(n+1), where i^2 = -1.

1, 2, 18, 560, 68642, 34215232, 69224885118, 564395560679680, 18462516899827251202, 2418515872778936155907072, 1267759411784533615311138990078, 2658525714048411732541898289615687680, 22300920657959489563024348304023741280501762, 748290577775586983580548698483165497859690809475072, 100433695860518615261304925954158931177362414164610493153278, 53919903879834365544910698161440014555837394338328471823987820789760

Offset

0,2

Comments

Notice that the imaginary components in the generating function vanish when expanded as a power series expansion in x.

Links

Table of n, a(n) for n=0..15.

Formula

G.f.: Sum_{n>=0} (2^n + i)^n * x^n / (1 + 2^n*i*x)^(n+1).

G.f.: Sum_{n>=0} (2^n - i)^n * x^n / (1 - 2^n*i*x)^(n+1).

a(n) = Sum_{k=0..n} i^k * binomial(n,k) * (2^n - 2^k*i)^(n-k).

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

Example

G.f.: A(x) = 1 + 2*x + 18*x^2 + 560*x^3 + 68642*x^4 + 34215232*x^5 + 69224885118*x^6 + 564395560679680*x^7 + 18462516899827251202*x^8 + ...
such that
A(x) = 1/(1+i*x) + (2 + i)*x/(1 + 2*i*x)^2 + (2^2 + i)^2*x^2/(1 + 2^2*i*x)^3 + (2^3 + i)^3*x^3/(1 + 2^3*i*x)^4 + (2^4 + i)^4*x^4/(1 + 2^4*i*x)^5 + (2^5 + i)^5*x^5/(1 + 2^5*i*x)^6 + (2^6 + i)^6*x^6/(1 + 2^6*i*x)^7 + ...
Also,
A(x) = 1/(1-i*x) + (2 - i)*x/(1 - 2*i*x)^2 + (2^2 - i)^2*x^2/(1 - 2^2*i*x)^3 + (2^3 - i)^3*x^3/(1 - 2^3*i*x)^4 + (2^4 - i)^4*x^4/(1 - 2^4*i*x)^5 + (2^5 - i)^5*x^5/(1 - 2^5*i*x)^6 + (2^6 - i)^6*x^6/(1 - 2^6*i*x)^7 + ...

Prog

(PARI) {a(n) = my(A = sum(m=0, n+1, (2^m + I)^m*x^m/(1 + I*2^m*x +x*O(x^n) )^(m+1) )); polcoeff(A, n)}
for(n=0, 20, print1(a(n), ", "))
(PARI) {a(n) = my(A = sum(m=0, n+1, (2^m - I)^m*x^m/(1 - I*2^m*x +x*O(x^n) )^(m+1) )); polcoeff(A, n)}
for(n=0, 20, print1(a(n), ", "))
(PARI) {a(n) = sum(k=0, n, I^k * binomial(n, k) * (2^n - 2^k*I)^(n-k) )}
for(n=0, 20, print1(a(n), ", "))
(PARI) {a(n) = sum(k=0, n, (-I)^k * binomial(n, k) * (2^n + 2^k*I)^(n-k) )}
for(n=0, 20, print1(a(n), ", "))

Crossrefs

Cf. A324306, A324307.

Sequence in context: A121936 A063389 A188202 * A071352 A258384 A296376

Adjacent sequences: A324305 A324306 A324307 * A324309 A324310 A324311

Keyword

nonn

Author

Paul D. Hanna, Mar 09 2019

Status

approved