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 A061727 A000217 interleaved with A061726. 2
 1, 4, 3, 12, 6, 30, 10, 50, 15, 60, 21, 84, 28, 140, 36, 180, 45, 180, 55, 220, 66, 330, 78, 390, 91, 364, 105, 420, 120, 600, 136, 680, 153, 612, 171, 684, 190, 950, 210, 1050, 231, 924, 253, 1012, 276, 1380, 300, 1500, 325, 1300, 351, 1404, 378, 1890, 406 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 REFERENCES Norman Sullivan, Test Your Own IQ, Workman Publishing Co. New York, NY, 1994, pp. 48, 50. LINKS Harry J. Smith, Table of n, a(n) for n = 1..2000 MATHEMATICA Array[{#, (4 + Boole[EvenQ@ #]) #} &@ PolygonalNumber@ # &, 28] // Flatten (* Michael De Vlieger, Jul 01 2018 *) PROG (PARI) { f="b061727.txt"; for (n=1, 1000, a=n*(n + 1)/2; if (a%2, t=a*4, t=a*5); write(f, 2*n - 1, " ", a); write(f, 2*n, " ", t) ) } \\ Harry J. Smith, Jul 27 2009 CROSSREFS Cf. A000217, A061726. Sequence in context: A106285 A240134 A193800 * A327916 A270025 A271199 Adjacent sequences:  A061724 A061725 A061726 * A061728 A061729 A061730 KEYWORD nonn,dumb,easy AUTHOR Jason Earls, May 05 2001 EXTENSIONS More terms from David Wasserman, Jun 25 2002 STATUS approved

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Last modified December 15 11:43 EST 2019. Contains 329999 sequences. (Running on oeis4.)