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A282084
Number of n-element subsets of [n+8] having an even sum.
2
1, 4, 20, 85, 255, 636, 1484, 3235, 6470, 12120, 21816, 37854, 63090, 101640, 159720, 245322, 367983, 540540, 780780, 1110395, 1554553, 2145572, 2925780, 3945045, 5260060, 6941168, 9076912, 11769100, 15131700, 19302480, 24449808, 30763812, 38454765, 47771700
OFFSET
0,2
LINKS
Index entries for linear recurrences with constant coefficients, signature (9, -41, 129, -316, 636, -1084, 1596, -2054, 2326, -2326, 2054, -1596, 1084, -636, 316, -129, 41, -9, 1).
FORMULA
G.f.: -(x^2-x+1)*(x^8-4*x^7+20*x^6-36*x^5+54*x^4-36*x^3+20*x^2-4*x+1) / ((x^2+1)^5*(x-1)^9).
a(n) = A282011(n+8,n).
EXAMPLE
a(0) = 1: {}.
a(1) = 4: {2}, {4}, {6}, {8}.
a(2) = 20: {1,3}, {1,5}, {1,7}, {1,9}, {2,4}, {2,6}, {2,8}, {2,10}, {3,5}, {3,7}, {3,9}, {4,6}, {4,8}, {4,10}, {5,7}, {5,9}, {6,8}, {6,10}, {7,9}, {8,10}.
CROSSREFS
Cf. A282011.
Sequence in context: A246936 A110154 A158608 * A262768 A250003 A343361
KEYWORD
nonn,easy
AUTHOR
Alois P. Heinz, Feb 05 2017
STATUS
approved