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.

A352240 Even numbers with at least one pair of Goldbach partitions, (p,q) and (r,s) with p,q,r,s prime and p < r <= s < q, such that all integers in the open intervals (p,r) and (s,q) are composite.

Original entry on oeis.org

10, 16, 18, 22, 24, 30, 34, 36, 42, 46, 48, 54, 60, 64, 66, 72, 76, 78, 82, 84, 90, 96, 98, 102, 106, 108, 110, 112, 114, 120, 126, 132, 136, 138, 140, 142, 144, 150, 154, 156, 160, 162, 168, 174, 180, 184, 186, 188, 190, 192, 194, 196, 198, 202, 204, 210, 216, 218, 220, 222
Offset: 1

Views

Author

Wesley Ivan Hurt, Mar 08 2022

Keywords

Comments

Similar to A187797 but also contains the numbers 82, 96, 98, 110, 136, ...

Examples

			82 is in the sequence since it has at least one pair of Goldbach partitions, namely (23,59) and (29,53), such that all integers in the open intervals (23,29) and (53,59) are composite.
		

Crossrefs

Programs

  • Mathematica
    Table[If[Sum[Sum[KroneckerDelta[NextPrime[k], i]*KroneckerDelta[NextPrime[2 n - i], 2 n - k]*(PrimePi[k] - PrimePi[k - 1]) (PrimePi[2 n - k] - PrimePi[2 n - k - 1]) (PrimePi[i] - PrimePi[i - 1]) (PrimePi[2 n - i] - PrimePi[2 n - i - 1]), {k, i}], {i, n}] > 0, 2 n, {}], {n, 150}] // Flatten

Formula

a(n) = A352442(n) + A352443(n).
a(n) = A352444(n) + A352445(n).

A352443 Smallest prime "s" among all pairs of Goldbach partitions of A352240(n), (p,q) and (r,s) with p,q,r,s prime and p < r <= s < q, such that all integers in the open intervals (p,r) and (s,q) are composite.

Original entry on oeis.org

5, 11, 11, 17, 13, 17, 29, 19, 29, 41, 29, 37, 31, 59, 43, 41, 47, 59, 53, 43, 53, 79, 61, 59, 53, 67, 73, 83, 61, 61, 73, 71, 83, 97, 73, 83, 97, 79, 149, 109, 131, 83, 97, 101, 97, 131, 103, 151, 131, 109, 157, 167, 127, 173, 103, 107, 109, 151, 131, 149, 157, 167, 127
Offset: 1

Views

Author

Wesley Ivan Hurt, Mar 16 2022

Keywords

Comments

See A352240.

Examples

			a(12) = 37; A352240(12) = 54 has 3 pairs of Goldbach partitions (7,47),(11,43); (11,43),(13,41); and (13,41),(17,37); with all integers composite in the open intervals (7,11) and (43,47), (11,13) and (41,43), and, (13,17) and (37,41) respectively. The smallest prime "s" among all Goldbach pairs is 37.
		

Crossrefs

Formula

a(n) = A352240(n) - A352442(n).

A352444 Largest prime "q" among all pairs of Goldbach partitions of A352240(n), (p,q) and (r,s) with p,q,r,s prime and p < r <= s < q, such that all integers in the open intervals (p,r) and (s,q) are composite.

Original entry on oeis.org

7, 13, 13, 19, 19, 23, 31, 31, 31, 43, 43, 47, 47, 61, 61, 61, 73, 73, 59, 73, 83, 83, 67, 83, 103, 103, 79, 109, 109, 113, 113, 113, 89, 131, 79, 139, 139, 139, 151, 151, 137, 151, 151, 167, 167, 181, 181, 157, 137, 181, 163, 193, 193, 199, 199, 199, 199, 157, 173, 193, 163
Offset: 1

Views

Author

Wesley Ivan Hurt, Mar 16 2022

Keywords

Comments

See A352240.

Examples

			a(12) = 47; A352240(12) = 54 has 3 pairs of Goldbach partitions (7,47),(11,43); (11,43),(13,41); and (13,41),(17,37); with all integers composite in the open intervals (7,11) and (43,47), (11,13) and (41,43), and, (13,17) and (37,41) respectively. The largest prime "q" among all Goldbach pairs is 47.
		

Crossrefs

Formula

a(n) = A352240(n) - A352445(n).

A352445 Smallest prime "p" among all pairs of Goldbach partitions of A352240(n), (p,q) and (r,s) with p,q,r,s prime and p < r <= s < q, such that all integers in the open intervals (p,r) and (s,q) are composite.

Original entry on oeis.org

3, 3, 5, 3, 5, 7, 3, 5, 11, 3, 5, 7, 13, 3, 5, 11, 3, 5, 23, 11, 7, 13, 31, 19, 3, 5, 31, 3, 5, 7, 13, 19, 47, 7, 61, 3, 5, 11, 3, 5, 23, 11, 17, 7, 13, 3, 5, 31, 53, 11, 31, 3, 5, 3, 5, 11, 17, 61, 47, 29, 61, 47, 29, 73, 3, 5, 73, 7, 3, 5, 11, 83, 17, 23, 37, 29, 3, 5, 23
Offset: 1

Views

Author

Wesley Ivan Hurt, Mar 16 2022

Keywords

Examples

			a(12) = 7; A352240(12) = 54 has 3 pairs of Goldbach partitions (7,47),(11,43); (11,43),(13,41); and (13,41),(17,37); with all integers composite in the open intervals (7,11) and (43,47), (11,13) and (41,43), and, (13,17) and (37,41) respectively. The smallest prime "p" among all Goldbach pairs is 7.
		

Crossrefs

Formula

a(n) = A352240(n) - A352444(n).
Showing 1-4 of 4 results.