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A243527
Prime numbers containing the string 111.
3
1117, 2111, 4111, 8111, 10111, 11113, 11117, 11119, 11131, 11149, 11159, 11161, 11171, 11173, 11177, 11197, 16111, 22111, 25111, 26111, 28111, 35111, 40111, 41113, 41117, 44111, 47111, 50111, 58111, 65111, 68111, 70111, 71119, 79111, 80111
OFFSET
1,1
LINKS
FORMULA
a(n) ~ n log n. - Charles R Greathouse IV, Jun 20 2014
MATHEMATICA
Select[Prime[Range[90000]], !StringFreeQ[ToString[#], "111"]&]
PROG
(PARI) contains(n, k)=my(N=digits(n), K=digits(k)); for(i=0, #N-#K, for(j=1, #K, if(N[i+j]!=K[j], next(2))); return(1)); 0
is(n)=isprime(n) && contains(n, 111) \\ Charles R Greathouse IV, Jun 20 2014
CROSSREFS
Cf. prime numbers containing the string kkk: this sequence (k=1), A166580 (k=2), A166581 (k=3), A166582 (k=4), A167281 (k=5), A131645 (k=6), A167282 (k=7), A167290 (k=8), A167292 (k=9).
Sequence in context: A221428 A161848 A020380 * A251360 A201034 A264312
KEYWORD
nonn,base,easy
AUTHOR
Vincenzo Librandi, Jun 06 2014
STATUS
approved