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A034187 Not necessarily symmetric n X 4 crossword puzzle grids. 7
1, 39, 649, 7943, 86995, 910667, 9339937, 94844591, 958363411, 9659847433, 97245624749, 978360244839, 9839915415611, 98949930968385, 994959069405031, 10004090931544495, 100586881489055547, 1011348141567934109 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Andrew Howroyd, Table of n, a(n) for n = 1..200

FORMULA

Empirical: a(n) = 24*a(n-1) - 218*a(n-2) + 1009*a(n-3) - 2623*a(n-4) + 3513*a(n-5) - 142*a(n-6) - 7707*a(n-7) + 11632*a(n-8) - 4443*a(n-9) - 6736*a(n-10) + 9655*a(n-11) - 3714*a(n-12) - 1529*a(n-13) + 1550*a(n-14) - 597*a(n-15) + 1041*a(n-16) + 195*a(n-17) - 150*a(n-18) + 8*a(n-19) + a(n-20) for n > 20. - Andrew Howroyd, Oct 02 2017

Empirical: x *(-1 -15*x +69*x^2 +140*x^3 -1117*x^4 +1696*x^5 +186*x^6 -1351*x^7 -1715*x^8 +3376*x^9 -52*x^10 -1829*x^11 +905*x^12 -1748*x^13 +446*x^14 -241*x^15 -72*x^16 +35*x^17 +7*x^18 +x^19) / ( (x^2+2*x-1) *(x^6 -7*x^5 +x^4 +6*x^3 -11*x^2 +7*x -1) *(x^12 +13*x^11 -71*x^10 +7*x^9 -113*x^8 +22*x^7 +222*x^6 -210*x^5 -19*x^4 +97*x^3 -59*x^2 +15*x -1) ). - R. J. Mathar, Jun 07 2020

CROSSREFS

Row 4 of A292357.

Column sums of A059680.

Cf. A001333, A034184, A034185, A034186, A034187.

Sequence in context: A142976 A200409 A341565 * A059609 A010955 A161652

Adjacent sequences:  A034184 A034185 A034186 * A034188 A034189 A034190

KEYWORD

nonn

AUTHOR

Erich Friedman

STATUS

approved

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Last modified March 4 23:02 EST 2021. Contains 341812 sequences. (Running on oeis4.)