A067791 Smallest multidigit prime such that the sum of the squares of its digits is equal to n times the product of its digits, or 0 if no such prime exists.

11353, 11, 211, 1111116211, 11411, 511111, 1111111111111111111111111111213, 11111117, 111111181, 1111111111111111111711, 2111111111111111111, 111111111111111121111, 1111111111111111111111141111111111111, 1111111111111111211111111

Offset

1,1

Comments

Sum(xi^2) = n*Product(xi) where xi is the i-th digit of a prime in base 10. The zero has been entered for those n values such that no solution has been found up to 10^7.

No more terms up to 4.4*10^11.

a(n) > (10^52-1)/9 for n = 18, 20, and 22. - Donovan Johnson

Links

Sean A. Irvine, Table of n, a(n) for n = 1..100

Sean A. Irvine, Java program (github)

Crossrefs

Sequence in context: A266181 A179917 A287245 * A067779 A202377 A210122

Adjacent sequences: A067788 A067789 A067790 * A067792 A067793 A067794

Keyword

nonn,base

Author

Felice Russo, Feb 06 2002

Extensions

a(8) and a(9) corrected by Charles R Greathouse IV, Nov 19 2010

a(4), a(7), a(10)-a(17), a(19), a(21) and a(23) from Donovan Johnson, Nov 20 2010

Status

approved