A250037 Numbers n such that m = floor(n/4) is not coprime to n and, if nonzero, m is also a term of the sequence.

2, 3, 8, 10, 12, 15, 32, 34, 40, 42, 48, 50, 51, 60, 63, 128, 130, 136, 138, 160, 162, 168, 170, 171, 192, 194, 195, 200, 202, 204, 207, 240, 242, 243, 252, 255, 512, 514, 520, 522, 544, 546, 552, 554, 555, 640, 642, 648, 650, 651, 672, 674, 675, 680, 682

Offset

1,1

Comments

See the comments in A250041 which all apply, except for the setting of the base, b=4. In particular, they define the property RTNC(b).

If x =12*k+j, 0 <= j <= 11, then x is in the sequence iff either j is in {0,2,3} and 3*k is in the sequence, or j is in {4,6} and 3*k+1 is in the sequence, or j is in {8,10} and 3*k+2 is in the sequence. - Robert Israel, Dec 22 2014

Links

Stanislav Sykora, Table of n, a(n) for n = 1..10000

Stanislav Sykora, PARI/GP scripts for genetic threads, with code and comments.

Wikipedia, Coprime integers

Maple

S:= {}:
for n from 1 to 1000 do
  m:= floor(n/4);
  if igcd(m, n) = 1 then next fi;
  if m > 0 and not member(m, S) then next fi;
  S:= S union {n}
od:
S; # if using Maple 11 or earlier, uncomment the next line
# sort(convert(S, list)); # Robert Israel, Dec 22 2014

Prog

(PARI) See the link.
(PARI) is_rtnc(n, b=4) = {while (((m=gcd(n\b, n)) != 1), if (m == 0, return (1)); n = n\b; ); return (0); } \\ Michel Marcus, Jan 22 2015

Crossrefs

Cf. A250036, A250041.

Other lists of right-truncatable numbers with the property RTNC(b):

A005823 (b=3), A250039 (b=16), A250041 (b=10), A250043 (b=9), A250045 (b=8), A250047 (b=7), A250049 (b=6), A250051 (b=5).

Sequence in context: A276559 A097053 A190668 * A360940 A132327 A281929

Adjacent sequences: A250034 A250035 A250036 * A250038 A250039 A250040

Keyword

nonn,base

Author

Stanislav Sykora, Dec 07 2014

Status

approved