A007379 Earliest sequence with a(a(n)) = 4n. (Formerly M0973)

0, 2, 4, 5, 8, 12, 7, 24, 16, 10, 36, 13, 20, 44, 15, 56, 32, 18, 68, 21, 48, 76, 23, 88, 28, 26, 100, 29, 96, 108, 31, 120, 64, 34, 132, 37, 40, 140, 39, 152, 144, 42, 164, 45, 52, 172, 47, 184, 80, 50, 196, 53, 176, 204, 55, 216, 60, 58, 228, 61, 224, 236, 63, 248

Offset

0,2

References

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Links

T. D. Noe, Table of n, a(n) for n = 0..1000

Index entries for sequences of the a(a(n)) = 2n family

Formula

a(8n)=4*a(2n), a(8n+1)=8n+2, a(8n+2)=32n+4, a(8n+3)=8n+5, a(8n+4)=4*a(2n+1), a(8n+5)=32n+12, a(8n+6)=8n+7, a(8n+7)=32n+24

Mathematica

a[n_] := a[n] = Which[ Mod[n, 8] == 0, 4*a[n/4], Mod[n, 8] == 1, n+1, Mod[n, 8] == 2, 4*(n-2)+4, Mod[n, 8] == 3, n+2, Mod[n, 8] == 4, 4*a[(n-4)/4+1], Mod[n, 8] == 5, 4*(n-5) + 12, Mod[n, 8] == 6, n+1, True, 4*(n-7)+24]; a[0] = 0; Table[ a[n], {n, 0, 63}] (* Jean-François Alcover, Sep 24 2012 *)

Crossrefs

Cf. A002516, A002517.

Sequence in context: A280017 A080136 A080033 * A080588 A032850 A190190

Adjacent sequences: A007376 A007377 A007378 * A007380 A007381 A007382

Keyword

nonn,nice

Author

Colin Mallows, N. J. A. Sloane, Mira Bernstein

Extensions

Formula and more terms from Henry Bottomley, Apr 27 2000

Status

approved