OFFSET

1,3

COMMENTS

This is the number of Fibonacci-style sequences seeded with positive integers that contain each n, after the seeds.

LINKS

Giovanni Resta, Table of n, a(n) for n = 1..10000

EXAMPLE

For n=4, a(4) = 4 as the sequences <1,3,4,7...>, <2,1,3,4...>, <2,2,4,6...>, and <3,1,4,5...> each contain 4 outside of the initial 2 numbers.

MATHEMATICA

a[n_] := Sum[Block[{s, L={x, y}}, While[(s = Total@L ) < n, L = Rest@ Append[L, s]]; If[s == n, 1, 0]], {x, n-1}, {y, n-x}]; Array[a, 65] (* Giovanni Resta, Aug 17 2015 *)

PROG

(PARI) isok(x, y, n) = {ny = 0; while (ny <= n, ny = x + y; if (ny == n, return (1)); x = y; y = ny; ); return (0); }

a(n) = {nb = 0; for (j=1, n-1, for (k=1, n-j, if (isok(j, k, n), nb++); ); ); nb; } \\ Michel Marcus, Aug 17 2015

CROSSREFS

KEYWORD

nonn

AUTHOR

Ben Johnsrude, Aug 16 2015

EXTENSIONS

More terms from Michel Marcus, Aug 17 2015

STATUS

approved