cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

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A209386 a(n) = 2*A005132(n).

Original entry on oeis.org

0, 2, 6, 12, 4, 14, 26, 40, 24, 42, 22, 44, 20, 46, 18, 48, 16, 50, 86, 124, 84, 126, 82, 36, 84, 34, 86, 32, 88, 30, 90, 28, 92, 158, 226, 156, 228, 154, 78, 156, 76, 158, 74, 160, 72, 162, 70, 164, 68, 166, 66, 168, 64, 170, 62, 172, 60, 174, 58, 176, 56, 178, 54, 180, 52, 182, 314, 448, 312, 450, 310
Offset: 0

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Author

N. J. A. Sloane, Mar 07 2012

Keywords

Comments

This is the even-numbers version of Recamán's sequence A005132: a(0)=0; for n>0, a(n) = a(n-1)-2n if that number is >= 0 and not already in the sequence, otherwise a(n) = a(n-1)+2n.

Links

Crossrefs

Cf. A005132, A209387.

Programs

  • Mathematica
    f[s_List]:= Block[{a = s[[-1]], len = Length@s}, Append[s, If[a > len && ! MemberQ[s, a - len], a - len, a + len]]]; A005132:= Nest[f, {0}, 130]; Table[2*A005132[[n]], {n, 1, 50}] (* G. C. Greubel, Jan 03 2018 *)
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Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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