A373912 - OEIS

A373912

Number of compositions of 7*n into parts 6 and 7.

1, 1, 1, 1, 1, 1, 2, 9, 37, 121, 331, 793, 1718, 3448, 6556, 12121, 22509, 43453, 89150, 193823, 436304, 989759, 2219064, 4869285, 10434412, 21900170, 45297211, 93054446, 191371581, 396480142, 830227401, 1756883373, 3746468095, 8017653633, 17151612398

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OFFSET

0,7

LINKS

Table of n, a(n) for n=0..34.

Index entries for linear recurrences with constant coefficients, signature (7,-21,35,-35,21,-6,1).

FORMULA

a(n) = A017847(7*n).

a(n) = Sum_{k=0..floor(n/6)} binomial(n+k,n-6*k).

a(n) = 7*a(n-1) - 21*a(n-2) + 35*a(n-3) - 35*a(n-4) + 21*a(n-5) - 6*a(n-6) + a(n-7).

G.f.: 1/(1 - x - x^6/(1 - x)^6).

PROG