A030670 - OEIS

A030670

Smallest prime whose decimal expansion begins (nontrivially) with the n-th prime.

23, 31, 53, 71, 113, 131, 173, 191, 233, 293, 311, 373, 419, 431, 479, 5323, 593, 613, 673, 719, 733, 797, 839, 8923, 971, 1013, 1031, 10711, 1091, 11311, 1277, 1319, 1373, 1399, 1493, 1511, 1571, 1637, 16729, 1733, 17911, 1811, 1913, 1931

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OFFSET

1,1

COMMENTS

Add digits to p (starting with a nonzero digit) until another prime is reached.

LINKS

Robert Israel, Table of n, a(n) for n = 1..10000

MAPLE

f:= proc(p) local d, x;

for d from 1 do

x:= nextprime(10^d*p+10^(d-1)-1);

if x < 10^d*(p+1) then return x fi

end proc:

map(f @ ithprime, [$1..100]); # Robert Israel, Aug 12 2018

MATHEMATICA

f[n_] := Block[{k = 1, p = Prime@ n}, While[a = 10^Floor[1 + Log10@ k] p + k; !PrimeQ@ a, k += 2]; a]; Array[f, 44]

CROSSREFS

See A064792 for another version. Note that A064792 <= a(n). Cf. A065112.

Sequence in context: A052230 A177981 A064792 * A030680 A330162 A006203

Adjacent sequences: A030667 A030668 A030669 * A030671 A030672 A030673

KEYWORD

nonn,base

AUTHOR

Patrick De Geest

STATUS

approved