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

1,2

Comments

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

Links

Table of n, a(n) for n=1..67.

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 *)

Crossrefs

Cf. A137576, A065091.

Sequence in context: A249064 A257489 A090252 * A242693 A119474 A308098

Adjacent sequences: A140137 A140138 A140139 * A140141 A140142 A140143

Keyword

nonn

Author

Vladimir Shevelev, May 10 2008

Extensions

Corrected and extended by Ray Chandler, May 19 2008

Status

approved