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A178327 Numbers k such that k^p+p is prime, where p is product of the digits of k. 1
1, 21, 6617, 12131, 12441, 114917, 121221, 124281, 125121, 145581, 172631, 182121, 191213, 211551, 221211, 221421, 241213, 293143, 421531, 421821 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
All terms are odd. Large numbers corresponding to some terms are probable
prime. There is no further term up to 27500.
254597 < a(18) <= 293143. a(19) <= 421531. a(20) <= 421821. - Donovan Johnson, Aug 09 2010
LINKS
EXAMPLE
21^(2*1)+(2*1) is prime so 21 is a term.
MATHEMATICA
Do[p=Apply[Times, IntegerDigits[n]]; If[PrimeQ[n^p+p], Print[n]],
{n, 1, 27501, 2}]
CROSSREFS
Sequence in context: A220552 A275053 A028451 * A231906 A250063 A307931
KEYWORD
base,more,nonn
AUTHOR
Farideh Firoozbakht, May 29 2010
EXTENSIONS
No more terms less than 56600. - Robert G. Wilson v, Jul 27 2010
a(6)-a(17) from Donovan Johnson, Aug 09 2010
a(18)-a(20) from Michael S. Branicky, Jun 23 2023
STATUS
approved

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Last modified May 23 16:36 EDT 2024. Contains 372765 sequences. (Running on oeis4.)