A269748 a(n) = 2*p+61+2*gcd(p-1,3)+gcd(p-1,4), where p = prime(n).

68, 71, 77, 83, 87, 97, 101, 107, 111, 125, 131, 145, 149, 155, 159, 173, 183, 193, 203, 207, 217, 227, 231, 245, 265, 269, 275, 279, 289, 293, 323, 327, 341, 347, 365, 371, 385, 395, 399, 413, 423, 433, 447, 457, 461, 467, 491, 515, 519, 529, 533, 543, 553, 567, 581, 591, 605, 611, 625, 629

Offset: 1

Author

N. J. A. Sloane, Mar 22 2016

Keywords

• nonn

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..1000
• Andrew Misseldine, Counting Schur Rings over Cyclic Groups, arXiv preprint arXiv:1508.03757 [math.RA], 2015.

Programs

Magma

[2*p+61 +2*Gcd(p-1,3)+Gcd(p-1,4): p in PrimesUpTo(700)]; // Vincenzo Librandi, Mar 26 2016

Maple

f1:=proc(n) local p; p:=ithprime(n);
2*p+61+2*gcd(p-1,3)+gcd(p-1,4);
end;

Mathematica

Table[2 Prime[n] + 61 + 2 GCD[Prime[n] - 1, 3] + GCD[Prime[n] -1, 4], {n, 60}] (* Vincenzo Librandi, Mar 26 2016 *)

Formula

a(n) = A232106(n) for n>=3. - R. J. Mathar, Jun 21 2025