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.

A217918 Positions of 2 in sequence A217916.

Original entry on oeis.org

1, 4, 11, 29, 46, 121, 172, 191, 254, 1276, 1432, 1654, 2416, 2486, 5254, 9181, 9592, 10012, 10441, 11629, 12881, 14029, 14197, 16472, 20707, 22367, 23872, 24532, 24977, 26336, 26797, 27496, 28681, 29162, 37951, 38227, 40756
Offset: 1

Views

Author

Paul D. Hanna, Mar 04 2013

Keywords

Crossrefs

Cf. A217916, A217919.

Formula

Involves triangular-indexed twin primes:
prime(a(n)) - prime(a(n)-1) = 2 for n>1 with a(1)=1.

A217919 Rows of A217916 in which 2's appear, when A217916 is formed into a number triangle.

Original entry on oeis.org

1, 3, 5, 8, 10, 16, 19, 20, 23, 51, 54, 58, 70, 71, 103, 136, 139, 142, 145, 153, 161, 168, 169, 182, 204, 212, 219, 222, 224, 230, 232, 235, 240, 242, 276, 277, 286
Offset: 1

Views

Author

Paul D. Hanna, Mar 04 2013

Keywords

Comments

The number 2 appears only in column 1 of A217916 (when treated as a triangle).

Crossrefs

Cf. A217916, A217918.

Formula

Involves triangular-indexed twin primes:
prime(a(n)*(a(n)-1)/2 + 1) - prime(a(n)*(a(n)-1)/2) = 2 for n>1 with a(1)=1.

A217917 Odd numbers that appear in sequence A217916.

Original entry on oeis.org

1, 5, 9, 11, 15, 17, 27, 29, 39, 41, 47, 49, 55, 61, 65, 69, 73, 79, 85, 89, 93, 111, 117, 119, 125, 137, 149, 153, 155, 161, 175, 181, 191, 193, 195, 211, 227, 231, 243, 255, 267, 269, 275, 279, 287, 295, 301, 307, 315, 317, 329, 335, 347, 349, 355, 357, 359, 361, 365
Offset: 1

Views

Author

Paul D. Hanna, Mar 04 2013

Keywords

Links

Crossrefs

Cf. A217916.

Formula

a(n) = A217916( (n+1)*(n+2)/2 - 1 ) for n>=1.

A217920 Column 1 of A217916 (when formed into a number triangle).

Original entry on oeis.org

2, 1, 2, 4, 2, 6, 6, 2, 6, 2, 6, 14, 4, 12, 6, 2, 4, 4, 2, 2, 6, 6, 2, 4, 6, 8, 6, 16, 6, 4, 6, 6, 6, 6, 6, 6, 14, 6, 6, 14, 10, 10, 8, 4, 12, 20, 8, 12, 6, 10, 2, 6, 14, 2, 14, 18, 6, 2, 6, 12, 4, 28, 6, 20, 6, 6, 6, 4, 16, 2, 2, 6, 4, 12, 6, 6, 6, 6, 8, 4, 6, 8, 6
Offset: 1

Views

Author

Paul D. Hanna, Mar 04 2013

Keywords

Comments

The number 2 appears in A217916 only in column 1.
The positions of 2 are given by A217919.

Links

Crossrefs

Cf. A217916, A217918, A217919.

Formula

a(n) = prime(n*(n-1)/2 + 1) - prime(n*(n-1)/2) for n>1 with a(1)=2.
Showing 1-4 of 4 results.

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

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