A140140 Positions of first appearances of odd primes in A137576.

1, 2, 3, 5, 4, 7, 9, 11, 14, 10, 18, 12, 21, 23, 26, 29, 17, 33, 35, 28, 39, 41, 42, 48, 50, 51, 53, 45, 43, 63, 46, 68, 69, 74, 38, 78, 66, 83, 86, 89, 90, 95, 59, 98, 85, 49, 111, 113, 97, 88, 119, 71, 125, 128, 131, 134, 135, 138, 93, 141, 146, 109, 155, 84, 158, 165, 145

Offset: 1

Author

Vladimir Shevelev, May 10 2008

Keywords

• nonn

Comments

a(n) <= (p_n-1)/2, where p_n is the n-th odd prime (A065091).

Crossrefs

Cf. A137576, A065091.

Programs

Mathematica

terms = 100;
a137576[n_] := Module[{t}, (t = MultiplicativeOrder[2, 2 n + 1])* DivisorSum[2 n + 1, EulerPhi[#]/MultiplicativeOrder[2, #] &] - t + 1];
A137576 = Array[a137576, 3 terms];
FirstPosition[A137576, #][[1]]& /@ Prime[Range[2, terms+1]] (* Jean-François Alcover, Jan 11 2019 *)

Extensions

Corrected and extended by Ray Chandler, May 19 2008