A007601 Positions where A007600 increases. (Formerly M0525)

1, 2, 3, 4, 5, 7, 10, 13, 19, 28, 37, 55, 82, 109, 163, 244, 325, 487, 730, 973, 1459, 2188, 2917, 4375, 6562, 8749, 13123, 19684, 26245, 39367, 59050, 78733, 118099, 177148, 236197, 354295, 531442, 708589, 1062883, 1594324, 2125765, 3188647

Offset

1,2

References

R. Honsberger, Mathematical Gems III, M.A.A., 1985, p. 225.

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

Links

Table of n, a(n) for n=1..42.

Eric Weisstein's World of Mathematics, Katona's Problem

Formula

a(n) = A000792(n-1)+1 for n>1. - Harry Altman, May 17 2011

Mathematica

f[n_] := Min[ Table[2p + 3Ceiling[Log[3, n/2^p]], {p, 0, 2}]]; g[1] = 1; g[n_] := g[n] = Block[{k = g[n - 1]}, While[ f[k] != n, k++ ]; k]; Table[ g[n], {n, 2, 15}] (* Robert G. Wilson v, Jan 15 2005 *)

Prog

(Python)
def A007601(n):
    if n == 1: return 1
    q, r = divmod(n-1, 3)
    return 1+int((3, 4, 6)[r]*3**(q-1)) # Chai Wah Wu, Jan 24 2026

Crossrefs

Cf. A000792, A007600.

Sequence in context: A018127 A017835 A390223 * A195944 A087830 A039857

Adjacent sequences: A007598 A007599 A007600 * A007602 A007603 A007604

Keyword

nonn,easy

Author

N. J. A. Sloane, Robert G. Wilson v, and Mira Bernstein

Extensions

More terms from Robert G. Wilson v, Jan 15 2005

Status

approved