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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A076848 Smallest prime factor of googol + n that exceeds 13, or 1 if googol + n is 13-smooth.

Original entry on oeis.org

73, 4832936419, 157, 20794121, 127, 859493, 557, 113, 3221, 19, 7549, 43, 17, 61, 211, 241, 18617, 907, 419, 47, 443, 911, 47955653711170550856726386495271851, 1109, 53, 31, 37, 2543, 19, 17, 617, 33521, 23, 7906914473, 38851, 421, 39640576062095087
Offset: 1

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Author

Jason Earls, Nov 23 2002

Keywords

Comments

A googol is 10^100. Factors found using PARI and Dario Alpern's ECM factorization applet.

Crossrefs

Cf. A049014 (n such that googol + n is prime), A066298, A080197 (relates to positions of 1's).
Equivalent sequences: A072288 (googolplex + n), A078813 (googol - n).
See the formula section for the relationships with A007947, A020639, A034386.

Formula

a(n) = A020639(A007947(10^100 + n)/gcd(10^100 + n, A034386(13))), where A020639(m) = lpf(m), smallest prime factor of m. - Peter Munn, Feb 20 2025

Extensions

a(23) found by Sean A. Irvine on Dec 08 2002 by employing SNFS, using the polynomials x^5+23 and x-10^20.
Edited by Robert G. Wilson v, Dec 09 2002
Edited by Peter Munn, Feb 20 2025
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