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A309747 Numbers k such that k^k + (k+1)^(k+1) is a semiprime. 0
5, 7, 9, 11, 14, 21, 37, 38, 39, 57, 90, 97, 162 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Numbers k such that A217435(k+1) = 2.
a(14) >= 235, see FactorDB link.
LINKS
Walter Nissen, Addendum to Prime factors of n^n + (n+1)^(n+1), Table F, 2014-01-07.
EXAMPLE
a(1) = 5 because 5^5 + 6^6 = 49781 = 67*743.
PROG
(PARI) for(k=0, 40, if(bigomega(k^k+(k+1)^(k+1))==2, print1(k, ", ")))
CROSSREFS
Sequence in context: A064077 A026282 A314375 * A080384 A086398 A356052
KEYWORD
nonn,more,hard
AUTHOR
Hugo Pfoertner, Aug 15 2019
STATUS
approved

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Last modified March 28 05:39 EDT 2024. Contains 371235 sequences. (Running on oeis4.)