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A333673
a(n) is the number of prime 5-digit palindromes in base n.
1
2, 3, 10, 18, 21, 41, 47, 64, 93, 106, 170, 171, 185, 227, 314, 345, 422, 464, 526, 571, 719, 806, 928, 972, 1179, 1237, 1354, 1508, 1754, 1778, 2116, 2108, 2401, 2529, 2862, 3010, 3188, 3362, 3580, 3820, 4218, 4330, 4817, 5033, 5488, 5516, 6225, 6343, 6759, 6870, 7497, 7704, 8151, 8660, 9267
OFFSET
2,1
COMMENTS
a(n) is the number of primes of the form a*(n^4+1)+b*(n^3+n)+c*n^2 where 1<=a<n, 0<=b<n and 0<=c<n.
LINKS
EXAMPLE
The a(4)=10 5-digit palindromes in base 4 are
257 = 10001_4
373 = 11311_4
409 = 12121_4
461 = 13031_4
509 = 13331_4
787 = 30103_4
839 = 31013_4
887 = 31313_4
907 = 32023_4
991 = 33133_4
MAPLE
f:= proc(n) nops(select(isprime, [seq(seq(seq(i*(n^4+1)+j*(n^3+n)+k*n^2, k=0..n-1), j=0..n-1), i=1..n-1)])) end proc:
map(f, [$2..60]);
CROSSREFS
Cf. A117752.
Sequence in context: A350913 A066915 A339924 * A070253 A147673 A298345
KEYWORD
nonn,base
AUTHOR
Robert Israel, May 04 2020
STATUS
approved