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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. 9
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 (list; graph; refs; listen; history; text; internal format)
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 * A132327 A281929 A286092

Adjacent sequences:  A250034 A250035 A250036 * A250038 A250039 A250040

KEYWORD

nonn,base

AUTHOR

Stanislav Sykora, Dec 07 2014

STATUS

approved

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Last modified May 22 16:19 EDT 2017. Contains 286882 sequences.