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A309238
Non-prime-square numbers equal to the sum of squares of consecutive primes from the least prime factor to the largest prime factor.
0
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
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
KEYWORD
nonn,more,bref
AUTHOR
Miroslav Kures, Jul 17 2019
STATUS
approved