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 A213250 Numbers n such that the coefficient of x^n in the expansion of Product_{k>=1} (1-x^k)^2 is zero. 7
 7, 11, 12, 17, 18, 21, 22, 25, 32, 37, 39, 41, 42, 43, 46, 47, 49, 54, 57, 58, 60, 62, 65, 67, 68, 72, 74, 75, 76, 81, 82, 87, 88, 90, 92, 95, 97, 98, 99, 106, 107, 109, 111, 112, 113, 116, 117, 120, 122, 123, 125, 126, 128, 130, 132, 136, 137 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Indices of zero entries in A002107. Asymptotic density is 1. Contains A093519, numbers with no representation as sum of two or fewer pentagonal numbers. LINKS Seiichi Manyama, Table of n, a(n) for n = 1..10000 MATHEMATICA LongPoly = Series[Product[1 - q^n, {n, 1, 300}]^2, {q, 0, 300}]; ZeroTable = {}; For[i = 1, i < 301, i++, If[Coefficient[LongPoly, q^i] == 0, AppendTo[ZeroTable, i]]]; ZeroTable PROG (PARI) x='x+O('x^200); v=Vec(eta(x)^2 - 1); for(k=1, #v, if(v[k]==0, print1(k, ", "))); /* Joerg Arndt, Jun 07 2012 */ CROSSREFS Cf. A093519. Numbers k such that the coefficient of x^k in the expansion of Product_{j>=1} (1 - x^j)^m is zero: A090864 (m=1), this sequence (m=2), A014132 (m=3), A302056 (m=4), A302057 (m=5), A020757 (m=6), A322043 (m=15). Sequence in context: A195608 A228523 A193301 * A226689 A117610 A176173 Adjacent sequences:  A213247 A213248 A213249 * A213251 A213252 A213253 KEYWORD easy,nonn AUTHOR William J. Keith, Jun 07 2012 STATUS approved

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Last modified January 24 16:47 EST 2020. Contains 331209 sequences. (Running on oeis4.)