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URL: https://oeis.org/A025180

⇱ A025180 - OEIS

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A025180
a(n) = number of (s(0), s(1), ..., s(n)) such that s(i) is an integer, s(0) = 0, |s(1)| = 1, |s(i) - s(i-1)| <= 1 for i >= 2, s(n) = 2. Also a(n) = T(n,n-2), where T is the array defined in A025177.
3
1, 2, 7, 20, 60, 176, 518, 1520, 4461, 13090, 38423, 112828, 331487, 974442, 2866125, 8434992, 24838275, 73181142, 215729781, 636275820, 1877569134, 5543095404, 16372140876, 48377825216, 143009973875, 422918975726, 1251154692297
OFFSET
2,2
FORMULA
Conjecture: -(n+2)*(n-3)*a(n) +2*(2*n+1)*(n-3)*a(n-1) +(-n^2+10*n-18)*a(n-2) -3*(2*n-3)*(n-3)*a(n-3)=0. - R. J. Mathar, Feb 25 2015
CROSSREFS
First differences of A014531. First differences are in A026069.
Sequence in context: A034899 A026124 A026153 * A201967 A116950 A111017
KEYWORD
nonn
STATUS
approved