A171733 a(2n)=A165568(n). a(2n+1)=A165563(n).

-1, 1, 1, 7, 31, 41, 137, 151, 391, 409, 889, 911, 1751, 1777, 3121, 3151, 5167, 5201, 8081, 8119, 12079, 12121, 17401, 17447, 24311, 24361, 33097, 33151, 44071, 44129, 57569, 57631, 73951, 74017, 93601, 93671, 116927, 117001, 144361, 144439, 176359, 176441, 213401, 213487, 255991

Offset

0,4

Links

Table of n, a(n) for n=0..44.

Index entries for linear recurrences with constant coefficients, signature (1,4,-4,-6,6,4,-4,-1,1).

Formula

a(n) = n^3/8 +n^2/16 -15/32 +n^4/16 +(-1)^n*( n^3/8+3*n^2/16-n-17/32 ).

G.f.: ( 1-2*x-4*x^2+2*x^3-18*x^4+2*x^5-4*x^6-2*x^7+x^8 ) / ( (1+x)^4*(-1+x)^5 ).

a(n)= +a(n-1) +4*a(n-2) -4*a(n-3) -6*a(n-4) +6*a(n-5) +4*a(n-6) -4*a(n-7) -a(n-8) +a(n-9).

Prog

(PARI) A171733(n)=if( bittest(n, 0), n, -1-n) +(n\=2)^2 +2*n^3 +n^4

Crossrefs

Cf. A035287.

Sequence in context: A309381 A276741 A000696 * A128028 A000921 A185004

Adjacent sequences: A171730 A171731 A171732 * A171734 A171735 A171736

Keyword

sign,easy

Author

Paul Curtz, Dec 17 2009

Status

approved