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 A089328 Smallest prime of the form the concatenation r*k for r = 1 to n followed by a 1. 2
 11, 241, 1231, 71421281, 2468101, 246810121, 244872961201441681, 8162432404856641, 1234567891, 10320630941251561872182492710301, 12345678910111, 12243648607284961081201321441, 43861291722152583013443874304735165591, 9418828237647056465875284694010341128122213161, 214263841051261471681892102312522732943151 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Robert Israel, Table of n, a(n) for n = 1..187 EXAMPLE a(3) = 1231 and k = 1. MAPLE dcat:= proc(L) local t, i; t:= L[1]; for i from 2 to nops(L) do t:= t*10^(1+ilog10(L[i]))+L[i] od: t end proc: f:= proc(n) local r, k, p; for k from 1 do p:= dcat([seq(r*k, r=1..n), 1]); if isprime(p) then return p fi od end proc: map(f, [\$1..20]); # Robert Israel, Apr 30 2018 CROSSREFS Cf. A089329. Sequence in context: A296170 A264465 A090921 * A077422 A267642 A267665 Adjacent sequences: A089325 A089326 A089327 * A089329 A089330 A089331 KEYWORD base,nonn AUTHOR Amarnath Murthy, Nov 04 2003 EXTENSIONS More terms from David Wasserman, Sep 13 2005 STATUS approved

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Last modified December 1 03:09 EST 2022. Contains 358454 sequences. (Running on oeis4.)