cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

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A305729 Numbers k such that A000010(k) = A023900(k) and A000010(A023900(k)) = A023900(A000010(k)).

Original entry on oeis.org

1, 14, 22, 46, 94, 118, 166, 214, 334, 358, 422, 454, 526, 662, 694, 718, 766, 926, 934, 958, 1006, 1094, 1126, 1142, 1174, 1382, 1438, 1678, 1718, 1726, 1774, 1822, 1934, 1966, 2038
Offset: 1

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Author

Torlach Rush, Aug 11 2018

Keywords

Comments

For known terms with n > 1:
- a(n) and phi(a(n)) are squarefree integers with an even number of prime factors. For example a(5) = 94 = 2 * 47, and phi(a(5)) = 46 = 2 * 23.
- When omega(a(n)) = omega(phi(a(n))) = 2 then a(n)/2 are the safe primes (see A005385).
- When omega(a(n)) = omega(phi(a(n))) = 2 then ((a(n)/2)-1)/2 = phi(a(n))/2 are the Sophie Germain primes (see A005384).

Examples

			1 is a term because A000010(1) = A023900(2) and A000010(A023900(1)) = A023900(A000010(1)).

Crossrefs

Cf. A000010, A023900, A005384, A005385.
Cf. Subsequence of A244466.
Cf. Subsequence of A306146.
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Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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