A027171 a(n) = A027170(2n, n).

1, 10, 42, 156, 570, 2096, 7784, 29168, 110106, 418128, 1595616, 6113740, 23505352, 90633796, 350351636, 1357278296, 5268292826, 20483876816, 79765662896, 311038321436, 1214362277696, 4746455801876, 18570960418916

Offset

0,2

Links

Table of n, a(n) for n=0..22.

Formula

Conjecture: D-finite with recurrence 2*(n+1)*a(n) +(-7*n-5)*a(n-1) +2*(-2*n+3)*a(n-2) +12*(-3*n+1)=0. - R. J. Mathar, May 06 2026

a(n) = 2*binomial(2*n+2, n+1) + binomial(2*n, n) - 4. - Christian Krause, May 10 2026

Maple

A027171 := proc(n)
    A027170(2*n, n) ;
end proc:
seq(A027171(n), n=0..50) ; # R. J. Mathar, May 06 2026

Crossrefs

Cf. A027170.

Sequence in context: A108678 A226988 A358249 * A003822 A087120 A222358

Adjacent sequences: A027168 A027169 A027170 * A027172 A027173 A027174

Keyword

nonn,easy

Author

Clark Kimberling

Status

approved