A074197 Let b(1) = n, b(k+1) = b(k)/2 + k if b(k) is even, b(k+1) = b(k)-k otherwise; sequence gives values of b(1) = n such that b(k) = 2k-4 for k large enough.

1, 11, 16, 18, 39, 44, 53, 57, 74, 102, 110, 111, 116, 125, 147, 152, 155, 160, 201, 218, 246, 273, 287, 289, 290, 292, 301, 306, 323, 328, 375, 380, 389, 391, 396, 398, 405, 507, 512, 542, 553, 570, 574, 598, 625, 642, 683, 688, 703, 708, 715, 717, 720, 729, 739, 744, 746

Offset

1,2

Links

Michel Marcus, Table of n, a(n) for n = 1..5000

Formula

a(n)/(n*log(n)) seems bounded and maybe a(n) is asymptotic to c*n*log(n) where 3 < c < 5.

Prog

(PARI) isok(m) = {my(N=1000, v=vector(N), prec=m, nb=0); v[1] = prec; for (n=2, N, v[n] = if (prec % 2, prec-n+1, prec/2+n-1); prec = v[n]; if (prec == 2*n-4, nb++); ); nb > N/10; } \\ Michel Marcus, Feb 16 2021

Crossrefs

Sequence in context: A097156 A138791 A132990 * A106673 A329389 A227080

Adjacent sequences: A074194 A074195 A074196 * A074198 A074199 A074200

Keyword

nonn

Author

Benoit Cloitre, Sep 16 2002

Extensions

More terms from Michel Marcus, Feb 15 2021

Status

approved