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 1-4 of 4 results.

A173015 Numbers k such that sequence of type a_k(n): {a(1) = 1, for n >= 2: a(n) = the smallest number h such that sigma(h) = A000203(h) = a(n-1) + k, a(n) = 0 if no such number exists} is sequence A063524(n) for n >= 1.

Original entry on oeis.org

9, 10, 16, 21, 22, 25, 26, 33, 34, 45, 46, 49, 50, 51, 52, 58, 64, 65, 66, 69, 70, 75, 76, 81, 82, 85, 86, 87, 88, 94, 99, 100, 105, 106, 115, 116, 117, 118, 122, 129, 130, 134, 135, 136, 141, 142, 145, 146, 147, 148, 153, 154, 165, 166, 169, 172, 177, 178, 184, 187, 188, 189, 190, 196
Offset: 1

Views

Author

Jaroslav Krizek, Nov 06 2010

Keywords

Comments

Sequence of composite numbers.
A063524(n) = characteristic function of 1 = 1,0,0,0,0,0,0,0,0,0,0,0, ...
Numbers k such that A051444(k) = A051444(k+1) = 0.
Complement of A173016.

Examples

			a(1) = k = 9 because a_9(n) = A063524(n) = 1,0,0,0,0,0,0,0,0,0,0,0, ...

Links

Crossrefs

Cf. A000035, A000203, A051444, A063524, A173012, A173013, A173014, A173016.

Programs

  • Mathematica
    seq[max_] := Module[{t = Table[1, {max}]}, t[[Complement[Range[max], Table[ DivisorSigma[1, n], {n, 1, max}]]]] = 0; SequencePosition[t, {0, 0}][[;; , 1]]]; seq[200] (* Amiram Eldar, Mar 22 2024 *)

Extensions

More terms from Amiram Eldar, Mar 22 2024

A173012 a(1) = 1, for n >= 2; a(n) = the smallest number h such that sigma(h) = A000203(h) = a(n-1) + 2, a(n) = 0 if no such number exists.

Original entry on oeis.org

1, 2, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
Offset: 1

Views

Author

Jaroslav Krizek, Nov 06 2010

Keywords

Comments

a(1) = 1, a(2) = 2, a(3) = 3, a(n) = 0 for n >= 4.

Crossrefs

Cf. A000035, A173013, A173014, A173015, A173016.

Programs

Formula

A000203(a(n)) = a(n-1) + 2 for n >= 2.

A173013 a(1) = 1, for n >= 2; a(n) = the smallest number h such that sigma(h) = A000203(h) = a(n-1) + 3, a(n) = 0 if no such number exists.

Original entry on oeis.org

1, 3, 5, 7, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2, 0, 2
Offset: 1

Views

Author

Jaroslav Krizek, Nov 06 2010

Keywords

Comments

a(n) is eventually periodic sequence with period (0, 2).

Crossrefs

Cf. A000035, A173012, A173014, A173015, A173016.

Programs

Formula

A000203(a(n)) = a(n-1) + 3 for n >= 2.

A173014 a(1) = 1, for n >= 2; a(n) = the smallest number h such that sigma(h) = A000203(h) = a(n-1) + 4, a(n) = 0 if no such number exists.

Original entry on oeis.org

1, 0, 3, 4, 7, 0, 3, 4, 7, 0, 3, 4, 7, 0, 3, 4, 7, 0, 3, 4, 7, 0, 3, 4, 7, 0, 3, 4, 7, 0, 3, 4, 7, 0, 3, 4, 7, 0, 3, 4, 7, 0, 3, 4, 7, 0, 3, 4, 7, 0, 3, 4, 7, 0, 3, 4, 7, 0, 3, 4, 7, 0, 3, 4, 7, 0, 3, 4, 7, 0, 3, 4, 7
Offset: 1

Views

Author

Jaroslav Krizek, Nov 06 2010

Keywords

Comments

a(1) = 1, a(n) = periodic sequence with period (0, 3, 4, 7) for n >= 2.

Crossrefs

Cf. A000035, A173012, A173013, A173015, A173016.

Programs

Formula

A000203(a(n)) = a(n-1) + 4 for n >= 2.
Showing 1-4 of 4 results.

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