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 A001010 Number of symmetric foldings of a strip of n stamps. (Formerly M0323 N0120) 4
 1, 2, 2, 4, 6, 8, 18, 20, 56, 48, 178, 132, 574, 348, 1870, 1008, 6144, 2812, 20314, 8420, 67534, 24396, 225472, 74756, 755672, 222556, 2540406, 693692, 8564622, 2107748, 28941258, 6656376, 98011464, 20548932 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 REFERENCES N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence). N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). LINKS Jean-François Alcover, Table of n, a(n) for n = 1..52 R. Dickau, Symmetric Stamp Foldings R. Dickau, Symmetric Stamp Foldings [Cached copy, pdf format, with permission] J. E. Koehler, Folding a strip of stamps, J. Combin. Theory, 5 (1968), 135-152. J. E. Koehler, Folding a strip of stamps, J. Combin. Theory, 5 (1968), 135-152. [Annotated, corrected, scanned copy] Frank Ruskey, Information on Stamp Foldings Eric Weisstein's World of Mathematics, Stamp Folding. FORMULA a(2n) = 2*A000682(n+2), a(2n+1) = 2*A007822(n). - Sean A. Irvine, Mar 18 2013 MATHEMATICA A000682 = Import["https://oeis.org/A000682/b000682.txt", "Table"][[All, 2]]; A007822 = Cases[Import["https://oeis.org/A007822/b007822.txt", "Table"], {_, _}][[All, 2]]; a[n_] := Which[n == 1, 1, EvenQ[n], 2*A000682[[n/2 + 1]], OddQ[n], 2*A007822[[(n - 1)/2 + 1]]]; Array[a, 52] (* Jean-François Alcover, Sep 03 2019, updated Jul 13 2022 *) CROSSREFS Cf. A007822, A000682. Sequence in context: A216214 A269298 A153964 * A357952 A091966 A231187 Adjacent sequences: A001007 A001008 A001009 * A001011 A001012 A001013 KEYWORD nonn,nice AUTHOR STATUS approved

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Last modified April 1 22:19 EDT 2023. Contains 361716 sequences. (Running on oeis4.)