A141230 Odd numbers n for which A006694((n-1)/2)=4.

15, 33, 39, 49, 55, 57, 81, 87, 95, 111, 113, 143, 159, 177, 183, 201, 209, 249, 281, 289, 295, 303, 319, 321, 335, 353, 393, 407, 415, 417, 447, 489, 519, 529, 535, 537, 543, 551, 577, 583, 591, 593, 617, 625, 633, 649, 655, 681, 695, 737, 767, 807, 815, 879, 895, 913, 951

Offset: 1

Author

Vladimir Shevelev, Jun 16 2008

Keywords

• nonn

Comments

If p>3 is a prime then 3p is in this sequence if and only if p is in A001122.

Crossrefs

Cf. A006694, A001122, A001134.

Programs

PARI

a006694(n)=sumdiv(2*n+1, d, eulerphi(d)/znorder(Mod(2, d))) - 1;
isok(n) = (n % 2) && (a006694((n-1)/2)== 4); \\ Michel Marcus, Dec 18 2018

Extensions

More terms from Michel Marcus, Dec 18 2018