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

1,1

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

Links

Table of n, a(n) for n=1..2.

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.

Example

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

Prog

(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

Crossrefs

Cf. A055233.

Sequence in context: A205984 A253748 A253755 * A153749 A186623 A202468

Adjacent sequences: A309235 A309236 A309237 * A309239 A309240 A309241

Keyword

nonn,more,bref

Author

Miroslav Kures, Jul 17 2019

Status

approved