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 A126883 a(n) = (2^0)*(2^1)*(2^2)*(2^3)...(2^n)-1 = 2^T(n) - 1 where T(n) = A000217(n) is the n-th triangular number. 3
 0, 1, 7, 63, 1023, 32767, 2097151, 268435455, 68719476735, 35184372088831, 36028797018963967, 73786976294838206463, 302231454903657293676543, 2475880078570760549798248447, 40564819207303340847894502572031, 1329227995784915872903807060280344575 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS For n > 2, a(n) and a(n-1) share at least one prime factor. Shows how many patterns can be created with 1-color thread while sewing on a button with buttonholes located on the vertices of a convex n-gon. - Ivan N. Ianakiev, Feb 09 2012 REFERENCES Masha Gessen, Perfect Rigor, A Genius and the Mathematical Breakthrough of the Century, Houghton Mifflin Harcourt, 2009, page 38. LINKS Muniru A Asiru, Table of n, a(n) for n = 0..80 FORMULA a(n) = A006125(n+1) - 1. - Zerinvary Lajos, Jun 12 2007 MAPLE seq(2^(binomial(2+n, n))-1, n=-1..12); # Zerinvary Lajos, Jun 12 2007 MATHEMATICA FoldList[Times, 2^Range[0, 20]]-1 (* Harvey P. Dale, Sep 09 2015 *) 2^Accumulate[Range[0, 20]]-1 (* Harvey P. Dale, Jun 03 2019 *) PROG (GAP) List([-1..15], n->2^(Binomial(2+n, n))-1); # Muniru A Asiru, Feb 21 2019 CROSSREFS Sequence in context: A084063 A184141 A152797 * A137810 A316577 A036287 Adjacent sequences:  A126880 A126881 A126882 * A126884 A126885 A126886 KEYWORD nonn AUTHOR Marco Matosic, Dec 29 2006 EXTENSIONS Corrected and extended by Harvey P. Dale, Sep 09 2015 STATUS approved

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Last modified February 26 12:33 EST 2020. Contains 332279 sequences. (Running on oeis4.)