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.

Showing 1-3 of 3 results.

A284698 Numbers k such that A284695(k) <= 3.

Original entry on oeis.org

1, 2, 3, 4, 6, 8, 9, 12, 16, 18, 24, 27, 36, 48, 54, 64, 72, 81, 108, 144, 162, 192, 216, 256, 324, 432, 512, 576, 648, 729, 768, 1296, 1458, 1536, 1728, 2304, 2916, 4096, 4608, 5184, 5832, 6561, 6912, 11664, 12288, 13122, 13824, 19683, 20736, 26244, 36864
Offset: 1

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Author

Rémy Sigrist, Apr 01 2017

Keywords

Comments

This sequence is a subsequence of the 3-smooth numbers (A003586).
This sequence could be interpreted as the "recursive" 3-smooth numbers.
If i and j belong to this sequence, then 2^i, 3^j and 2^i*3^j also belong to this sequence.
This sequence contains the nonzero values in A014221 and in A014222.

Examples

			1762613844998129336721604608 = 2^3^(2^2) * 3^(2*3) appears in this sequence.

Links

Crossrefs

Cf. A003586, A014221, A014222, A284695.

A284694 Least prime number appearing in the prime tower factorization of n (when n > 1); a(1) = 1.

Original entry on oeis.org

1, 2, 3, 2, 5, 2, 7, 2, 2, 2, 11, 2, 13, 2, 3, 2, 17, 2, 19, 2, 3, 2, 23, 2, 2, 2, 3, 2, 29, 2, 31, 2, 3, 2, 5, 2, 37, 2, 3, 2, 41, 2, 43, 2, 2, 2, 47, 2, 2, 2, 3, 2, 53, 2, 5, 2, 3, 2, 59, 2, 61, 2, 2, 2, 5, 2, 67, 2, 3, 2, 71, 2, 73, 2, 2, 2, 7, 2, 79, 2, 2
Offset: 1

Views

Author

Rémy Sigrist, Apr 01 2017

Keywords

Comments

See A182318 for the definition of the prime tower factorization of a number.
a(n) <= A020639(n) for any n>0.

Examples

			9 = 3^2, hence a(9) = min(3, 2) = 2.

Links

Crossrefs

Cf. A020639, A182318, A279513, A284695.

Formula

a(n) = A020639(A279513(n)) for any n>0.

A284696 Numbers of the form p^^k, with p prime and k>=0, where ^^ denotes tetration.

Original entry on oeis.org

1, 2, 3, 4, 5, 7, 11, 13, 16, 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
Offset: 1

Views

Author

Rémy Sigrist, Apr 01 2017

Keywords

Comments

Also numbers n such that A284694(n)=A284695(n).
Also numbers with no distinct prime numbers in their prime tower factorization (see A182318 for the definition of the prime tower factorization of a number).
Also numbers n such that A279513(n) is a power of prime (A000961).
This sequence is the union of 1, the prime numbers (A000040), and A275211.

Examples

			16 = 2^^3 is in the sequence.

Links

Crossrefs

Cf. A000040, A000961, A182318, A275211, A279513, A284694, A284695.
Showing 1-3 of 3 results.

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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