A367660 - OEIS

A367660

G.f. A(x) satisfies A(x) = 1 / (1 - x - x * A(x^4)).

1, 2, 4, 8, 16, 34, 72, 152, 320, 676, 1428, 3016, 6368, 13448, 28400, 59976, 126656, 267472, 564848, 1192848, 2519056, 5319746, 11234248, 23724504, 50101440, 105804296, 223437672, 471856016, 996466240, 2104338904, 4443946064, 9384731992, 19818691136

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OFFSET

0,2

LINKS

Table of n, a(n) for n=0..32.

FORMULA

a(0) = 1; a(n) = a(n-1) + Sum_{k=0..floor((n-1)/4)} a(k) * a(n-1-4*k).

a(0) = 1, a(1) = 2, a(2) = 4, a(3) = 8; a(n) = a(n-4) + Sum_{k=0..n-1} a(floor(k/4)) * a(n-1-k).

PROG

(PARI) a_vector(n) = my(v=vector(n+1)); v[1]=1; for(i=1, n, v[i+1]=v[i]+sum(j=0, (i-1)\4, v[j+1]*v[i-4*j])); v;

CROSSREFS

Cf. A349365, A367659, A367661.