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A258217
Smallest multiple of 7 starting with n, that did not appear earlier.
4
14, 21, 35, 42, 56, 63, 7, 84, 91, 105, 112, 126, 133, 140, 154, 161, 175, 182, 196, 203, 210, 224, 231, 245, 252, 266, 273, 28, 294, 301, 315, 322, 336, 343, 350, 364, 371, 385, 392, 406, 413, 420, 434, 441, 455, 462, 476, 483, 49, 504, 511, 525, 532, 546
OFFSET
1,1
COMMENTS
The sequence is a permutation of the positive multiples of 7. - Vladimir Shevelev, May 24 2015
A258334(n) = a(n) / 7 is a permutation of the positive integers. - Reinhard Zumkeller, May 27 2015
LINKS
Éric Angelini, Multiples of 3 ending with n, SeqFan list, May 23 2015.
MATHEMATICA
a[1] = 14; a[n_] := a[n] = For[dn = IntegerDigits[n]; k = 7, True, k = k+7, dk = IntegerDigits[k]; lg = Min[Length[dn], Length[dk]]; If[Union[ Take[dk, lg] - Take[dn, lg]] == {0} && FreeQ[Array[a, n-1], k], Return[k]]]; Array[a, 54] (* Jean-François Alcover, Feb 09 2018 *)
PROG
(Haskell)
import Data.List (isPrefixOf, delete)
a258217 n = a258217_list !! (n-1)
a258217_list = f 1 $ tail $ zip a008589_list $ map show a008589_list where
f x ws = g ws where
g ((u, vs) : uvs) = if isPrefixOf (show x) vs
then u : f (x + 1) (delete (u, vs) ws) else g uvs
CROSSREFS
KEYWORD
nonn,base
AUTHOR
STATUS
approved