A187605
Primes of the form k^k + k - 1.
Original entry on oeis.org
5, 29, 1978419655660313589123997, 205891132094649000000000000000000000000000029
Offset: 1
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Do[p=n^n+n-1; If[PrimeQ[p], Print[p]], {n, 100}]
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lista(nn) = for(k=1, nn, if(ispseudoprime(q=k^k+k-1), print1(q, ", "))); \\ Jinyuan Wang, Mar 01 2020
A342449
a(n) = Sum_{k=1..n} gcd(k,n)^k.
Original entry on oeis.org
1, 5, 29, 262, 3129, 46705, 823549, 16777544, 387421251, 10000003469, 285311670621, 8916100581446, 302875106592265, 11112006826387025, 437893890391180013, 18446744073743123788, 827240261886336764193, 39346408075299116257065
Offset: 1
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a[n_] := Sum[GCD[k, n]^k, {k, 1, n}]; Array[a, 20] (* Amiram Eldar, Mar 13 2021 *)
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a(n) = sum(k=1, n, gcd(k, n)^k);
A357055
Integers k such that k^k + k^2 + 3*k + 2 is prime.
Original entry on oeis.org
0, 1, 3, 5, 11, 209, 1281
Offset: 1
For k = 3, k^k + k^2 + 3*k + 2 = 47 and 47 is prime.
A357056
Integers k such that k^k + k^2 + 2*k + 1 is prime.
Original entry on oeis.org
0, 1, 2, 3, 4, 9, 10, 13, 15, 24
Offset: 1
If k = 2, then k^k + k^2 + k*2 + 1 = 2^2 + 2^2 + 2*2 + 1 = 13, which is prime.
Showing 1-4 of 4 results.
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