cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

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A202136 Prefixing digits to Mersenne primes to obtain larger primes.

Original entry on oeis.org

13, 17, 131, 4127, 18191, 10131071, 1524287, 362147483647, 152305843009213693951, 58618970019642690137449562111, 57162259276829213363391578010288127, 55170141183460469231731687303715884105727
Offset: 1

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Author

Gilbert Mozzo, Dec 12 2011

Keywords

Comments

The smallest prefixing digits for the Mersenne primes are given in A209385. - Gilbert Mozzo, Mar 07 2012
The next term a(13) has 160 decimal digits. - Andrew Howroyd, Nov 17 2018

Examples

			For Mersenne4: -1 + 2^7 + 4*10^3 = 4127 which is prime.

Links

Crossrefs

Cf. A000668, A209385.

Programs

  • PARI
    ppfx(n)={my(w=10^(1+logint(n,10)), k=n+w); while(!ispseudoprime(k), k+=w); k}
{ for(n=1, 100, my(p=1<Andrew Howroyd, Nov 17 2018

Formula

Mersenne prime + n*10^D with D = number of digits of the Mersenne prime.

Extensions

a(7)-a(9) added by Gilbert Mozzo, Mar 07 2012
a(10)-a(12) from Andrew Howroyd, Nov 17 2018
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