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A141164
Numbers having exactly 1 divisor of the form 8*k + 7.
11
7, 14, 15, 21, 23, 28, 30, 31, 35, 39, 42, 45, 46, 47, 49, 55, 56, 60, 62, 69, 70, 71, 75, 77, 78, 79, 84, 87, 90, 91, 92, 93, 94, 95, 98, 103, 110, 111, 112, 115, 117, 120, 124, 127, 133, 138, 140, 141, 142, 143, 147, 150, 151, 154, 155, 156, 158, 159, 167, 168, 174, 180, 182, 183, 184, 186, 188, 190, 191, 196, 199
OFFSET
1,1
LINKS
FORMULA
A188172(a(n)) = 1.
EXAMPLE
a(1) = A188226(1) = 7.
MATHEMATICA
okQ[n_] := Length[Select[Divisors[n] - 7, Mod[#, 8] == 0 &]] == 1; Select[Range[200], okQ]
PROG
(Haskell)
import Data.List (elemIndices)
a141164 n = a141164_list !! (n-1)
a141164_list = map succ $ elemIndices 1 $ map a188172 [1..]
(PARI) res(n, a, b) = sumdiv(n, d, (d%a) == b)
isA141164(n) = (res(n, 8, 7) == 1) \\ Jianing Song, Apr 06 2021
CROSSREFS
Numbers having m divisors of the form 8*k + i: A343107 (m=1, i=1), A343108 (m=0, i=3), A343109 (m=0, i=5), A343110 (m=0, i=7), A343111 (m=2, i=1), A343112 (m=1, i=3), A343113 (m=1, i=5), this sequence (m=1, i=7).
Indices of 1 in A188172.
A007522 is a subsequence.
Cf. A004771.
Sequence in context: A297138 A085335 A069137 * A004781 A004759 A364287
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Mar 26 2011
STATUS
approved