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A089720 Primes p ending in 1 such that floor(p/7) = 0, 1 or 2 (mod 10). 0
11, 71, 151, 211, 281, 421, 431, 491, 571, 631, 641, 701, 911, 991, 1051, 1061, 1201, 1471, 1481, 1621, 1831, 1901, 2111, 2251, 2311, 2381, 2521, 2531, 2591, 2671, 2731, 2741, 2801, 3011, 3221, 3301, 3361, 3371, 3511, 3571, 3581, 3851, 3931, 4001, 4201 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Original definition: Pseudofactor sets of primes ending in 1: 7 less than 3.

A prime ending in 1 is listed as a[n] if Mod(floor(a[n]/7),10) < 3, where Mod() is the binary "remainder" operator.

LINKS

Table of n, a(n) for n=1..45.

MATHEMATICA

digits=4*200 a=Delete[Union[Table[If[Mod[Prime[n], 10]==1, Prime[n], 0], {n, 1, digits}]], 1] d2=Dimensions[a][[1]] a7l3=Delete[Union[Table[If[Mod[a[[n]]/7, 10]<3, a[[n]], 0], {n, 1, d2}]], 1]

okQ[n_]:=Mod[n, 10]==1&&MemberQ[{0, 1, 2}, Mod[Floor[n/7], 10]]; Select[Prime[ Range[600]], okQ] (* Harvey P. Dale, Oct 16 2012 *)

PROG

(PARI) forprime( p=1, 9999, p%10==1 & p\7%10<3 & print1(p", ")) \\ M. F. Hasler, Apr 06 2009

CROSSREFS

Sequence in context: A162568 A255205 A117047 * A333408 A174202 A139850

Adjacent sequences:  A089717 A089718 A089719 * A089721 A089722 A089723

KEYWORD

nonn,base

AUTHOR

Roger L. Bagula, Jan 06 2004

EXTENSIONS

Edited by M. F. Hasler, Apr 06 2009

STATUS

approved

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Last modified March 28 05:38 EDT 2020. Contains 333073 sequences. (Running on oeis4.)