A272693 a(0)=0; thereafter, a(n) = (A108618(n-1)-3*A108619(n))/2.

0, -1, -2, -5, -4, -3, -3, 0, 5, 2, -3, -6, -7, -5, 2, 9, 4, -5, -10, -9, -3, 6, 11, 5, -10, -21, -12, 5, 14, 9, -5, -19, -17, -4, 15, 16, 1, -15, -21, -12, 11, 20, 9, -11, -25, -17, 2, 21, 16, -5, -22, -21, -3, 18, 23, 5, -22, -33, -15, 18, 35, 17, -22, -45, -24, 17, 38, 21, -17, -43, -29, 8, 39

Offset: 0

Author

N. J. A. Sloane, Jun 07 2016

Keywords

• sign

Links

• N. J. A. Sloane, Table of n, a(n) for n = 0..10000

Crossrefs

Cf. A108618, A108619.

Programs

Maple

M:=1000;
a:=Array(0..M,0); # A108618 (with different offset)
b:=Array(0..M,0); # A108619 (with different offset)
c:=Array(0..M,0); # A272693
f:=n->sign(n)*(n mod 2);
a[0]:=0; b[0]:=0; c[0]:=0;
for n from 1 to M do
b[n]:=1+(a[n-1]+b[n-1])/2;
a[n]:=1+c[n-1]+f(c[n-1])+3*f(b[n]-1);
c[n]:=(a[n]-3*b[n])/2;
od:
[seq(a[n],n=0..M)];
[seq(b[n],n=0..M)];
[seq(c[n],n=0..M)];