Emanuele Pace - cp's OEIS frontend

User: Emanuele Pace

Emanuele Pace has authored 2 sequences.

A384227 Smaller members p of sexy prime pairs (p,p+6) such that both p and p+6 are emirps.

31, 73, 107, 733, 1091, 1097, 1103, 1217, 1223, 1231, 3083, 3163, 3251, 3463, 3911, 7187, 7523, 7643, 7681, 9127, 9221, 9491, 9781, 10061, 10247, 10453, 10853, 10987, 11587, 11777, 11783, 11833, 11897, 11903, 11927, 11933, 11953, 12107, 12113, 12547, 12757

Offset: 1

Emanuele Pace, Aug 26 2025

Cf. A006567, A023201.

emirpQ[n_] := emirpQ[n] = n != IntegerReverse[n] && PrimeQ[n] && PrimeQ[IntegerReverse[n]]; Select[Range[13000], emirpQ[#] && emirpQ[# + 6] &] (* Amiram Eldar, Aug 26 2025 *)

A387107 a(n) = psi(2^n-1), where psi = A002322.

Original entry on oeis.org

1, 2, 6, 4, 30, 6, 126, 16, 72, 30, 88, 12, 8190, 126, 150, 256, 131070, 72, 524286, 120, 1008, 2728, 178480, 240, 1800, 8190, 262656, 1008, 39672, 1650, 2147483646, 65536, 2397912, 131070, 1106280, 216, 616318176, 524286, 12743640, 61680, 26815350376, 43344, 1186422030

Offset: 1

Emanuele Pace, Aug 16 2025

Cf. A002322, A000225.

a[n_] := CarmichaelLambda[2^n - 1]; Array[a, 50] (* Amiram Eldar, Aug 16 2025 *)

a(n) = lcm(znstar(2^n-1)[2]); \\ Michel Marcus, Aug 22 2025

a(n) = A002322(A000225(n)).

cp's OEIS Frontend

User: Emanuele Pace

A384227 Smaller members p of sexy prime pairs (p,p+6) such that both p and p+6 are emirps.

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