A225648 Positions of ones in A225650, numbers n such that n and A000793(n) are coprime.

0, 1, 5, 7, 8, 9, 11, 13, 17, 19, 23, 27, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271, 277, 281, 283, 293, 307, 311, 313

Offset

1,3

Comments

Contains all primes from 5 onward. Are 8, 9 and 27 only composite numbers present?

Links

Alois P. Heinz, Table of n, a(n) for n = 1..5000

Mathematica

b[n_, i_] := b[n, i] = Module[{p}, p = If[i < 1, 1, Prime[i]]; If[n == 0 || i < 1, 1, Max[b[n, i - 1], Table[p^j*b[n - p^j, i - 1], {j, 1, Log[p, n] // Floor}]]]]; g[n_] := b[n, If[n < 8, 3, PrimePi[Ceiling[1.328*Sqrt[n* Log[n] // Floor]]]]]; Join[{0}, Position[Table[GCD[n, g[n]], {n, 1, 500} ], 1] // Flatten] (* Jean-François Alcover, Mar 03 2016, after Alois P. Heinz *)

Prog

(Scheme with Antti Karttunen's IntSeq-library):
(define A225648 (MATCHING-POS 1 1 (lambda (i) (= 1 (gcd (A000793 i) i)))))

Crossrefs

Complement: A225649. Cf. also A225650.

Sequence in context: A118742 A122904 A104693 * A031221 A137469 A043353

Adjacent sequences: A225645 A225646 A225647 * A225649 A225650 A225651

Keyword

nonn

Author

Antti Karttunen, May 12 2013

Status

approved