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 A135882 Column 1 of triangle A135880. 6
 1, 2, 7, 34, 215, 1698, 16220, 182714, 2378780, 35219202, 585245185, 10797322816, 219163958124, 4856832298391, 116735215192864, 3025759884533190, 84155831914971391, 2500599947944218716, 79072271422935678302 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS Paul D. Hanna, Table of n, a(n) for n = 0..79 EXAMPLE Equals column 1 of triangle P=A135880: 1; 1, 1; 2, 2, 1; 6, 7, 3, 1; 25, 34, 15, 4, 1; 138, 215, 99, 26, 5, 1; 970, 1698, 814, 216, 40, 6, 1; ... where column k of P^2 equals column 0 of P^(2k+2) such that column 0 of P^2 equals column 0 of P shift left. PROG (PARI) {a(n)=local(P=Mat(1), R, PShR); if(n==0, 1, for(i=0, n, PShR=matrix(#P, #P, r, c, if(r>=c, if(r==c, 1, if(c==1, 0, P[r-1, c-1])))); R=P*PShR; R=matrix(#P+1, #P+1, r, c, if(r>=c, if(r<#P+1, R[r, c], if(c==1, (P^2)[ #P, 1], (P^(2*c-1))[r-c+1, 1])))); P=matrix(#R, #R, r, c, if(r>=c, if(r<#R, P[r, c], (R^c)[r-c+1, 1])))); P[n+2, 2])} CROSSREFS Cf. A135880; other columns: A135881, A135883, A135884. Sequence in context: A177401 A171792 A185324 * A143740 A049463 A029894 Adjacent sequences:  A135879 A135880 A135881 * A135883 A135884 A135885 KEYWORD nonn AUTHOR Paul D. Hanna, Dec 15 2007 EXTENSIONS Error in entries (false comma) corrected by N. J. A. Sloane, Jan 23 2008 STATUS approved

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