A309238 Non-prime-square numbers equal to the sum of squares of consecutive primes from the least prime factor to the largest prime factor.

315797, 9634877

Offset: 1

Author

Miroslav Kures, Jul 17 2019

Keywords

• nonn
• more
• bref

Comments

So-called 2-straddled numbers; 1-straddled numbers are in A055233.

a(3) > 7*10^14, if it exists. - Giovanni Resta, Jul 18 2019

Examples

			9634877 = 7 * 41 * 59 * 569 = 7^2 + 11^2 + 13^2 + ... + 569^2.
		

Links

• M. Kures, Straddled numbers: numbers equal to the sum of powers of consecutive primes from the least prime factor to the largest prime factor, Notes on Number Theory and Discrete Mathematics, 2019, vol. 25, no. 2, pp. 8-15. ISSN: 1310-5132.

Crossrefs

Cf. A055233.

Programs

PARI

isok(n) = if (isprimepower(n) != 2, if (n>1, my(f=factor(n)[,1], s=0); forprime(p=vecmin(f), vecmax(f), s+= p^2); s == n)); \\ Michel Marcus, Jul 18 2019