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 A013580 Triangle formed in same way as Pascal's triangle (A007318) except 1 is added to central element in even-numbered rows. 3
 1, 1, 1, 1, 3, 1, 1, 4, 4, 1, 1, 5, 9, 5, 1, 1, 6, 14, 14, 6, 1, 1, 7, 20, 29, 20, 7, 1, 1, 8, 27, 49, 49, 27, 8, 1, 1, 9, 35, 76, 99, 76, 35, 9, 1, 1, 10, 44, 111, 175, 175, 111, 44, 10, 1, 1, 11, 54, 155, 286, 351, 286, 155, 54, 11, 1, 1, 12, 65, 209, 441, 637, 637, 441, 209, 65 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 0,5 LINKS G. C. Greubel, Table of n, a(n) for the first 50 rows, flattened FORMULA G.f.: 1/(1-(1+y)*x)/(1-y*x^2). - Vladeta Jovovic, Oct 12 2003 EXAMPLE 1; 1, 1; 1, 3, 1; 1, 4, 4, 1; 1, 5, 9, 5, 1; ... MATHEMATICA CoefficientList[CoefficientList[Series[1/(1 - (1 + y)*x)/(1 - y*x^2), {x, 0, 10}, {y, 0, 10}], x], y] // Flatten (* G. C. Greubel, Oct 10 2017 *) CROSSREFS Row sums give A000975, A054106. Sequence in context: A028262 A173117 A050177 * A147290 A026670 A131402 Adjacent sequences:  A013577 A013578 A013579 * A013581 A013582 A013583 KEYWORD tabl,nonn,easy AUTHOR Martin Hecko (bigusm(AT)interramp.com) EXTENSIONS More terms from James A. Sellers STATUS approved

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Last modified May 26 09:58 EDT 2019. Contains 323579 sequences. (Running on oeis4.)