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.

Previous Showing 11-15 of 15 results.

A069455 Greater of lonely twin primes.

Original entry on oeis.org

31, 43, 61, 73, 229, 241, 271, 283, 313, 349, 463, 523, 571, 601, 619, 643, 661, 859, 883, 1093, 1153, 1231, 1279, 1291, 1303, 1321, 1429, 1453, 1609, 1621, 1669, 1699, 1723, 1789, 1999, 2029, 2143, 2239, 2269, 2311, 2341, 2383
Offset: 1

Views

Author

Neil Fernandez, Mar 22 2002

Keywords

Examples

			The first lonely twin primes (A069453) are 29,31 (23 and 37 are non-twin), 41,43 (37 and 47 are non-twin), 59,61 (53 and 67 are non-twin). Of these, the greater twins are 31,43,61, so this is how the sequence begins.
		

Crossrefs

A262936 Lesser of lonely twin primes pairs with increasing distance to nearest prime.

Original entry on oeis.org

3, 5, 11, 29, 419, 521, 1931, 6449, 10007, 28349, 107507, 173429, 569321, 913637, 1349531, 3593201, 18286391, 80528741, 83528411, 591792347, 1971409091, 2061246347, 8579208791, 13861166687, 15250041281, 27034148369, 27066034997, 54125499299, 315361055237
Offset: 1

Views

Author

Dmitry Petukhov, Oct 04 2015

Keywords

Examples

			(3,5) is a twin primes pair, min(7-5, 3-2)=1, therefore a(1)=3.
(5,7) is a twin primes pair, min(11-7, 5-3)=2>1, therefore a(2)=5.
(11,13) is a twin primes pair, min(17-13, 11-7)=4>2, therefore a(3)=11.
		

Crossrefs

Subsequence of A001359.

Programs

  • PARI
    {m=0; q=5; s=3; t=2; forprime(p=6, 10^9, if((q-s==2) && (min(p-q, s-t)>m), m=min(p-q, s-t); print1(s, ", ") ); t=s; s=q; q=p;)}

Formula

a(n) = p(i) if ( (p(i+1) = p(i)+2) AND (min(p(i+2)-p(i+1), p(i)-p(i-1)) > a(n-1)) ), where a(0) = 0, p(k) = prime(k) = A000040(k).

A259034 Start of a string of exactly 9 consecutive (but disjoint) pairs of twin primes.

Original entry on oeis.org

170669145704411, 597655503030737, 1209758169609917, 1529543606818727, 1980326398382819, 2752137854763287, 3748062700238369, 4071945430128767, 4518517172328671, 4662894516572177, 5979435335619701, 6264049608329957, 7609375387833677, 8064845880680819
Offset: 1

Views

Author

Dmitry Petukhov, Nov 08 2015

Keywords

Crossrefs

Extensions

Terms a(6) and beyond from Tomáš Brada, Jun 04 2020

A262935 Increasing distances of lonely twin primes pairs to nearest prime.

Original entry on oeis.org

1, 2, 4, 6, 10, 12, 16, 18, 28, 30, 34, 42, 46, 48, 58, 88, 90, 94, 124, 130, 136, 154, 162, 168, 172, 178, 202, 216, 258, 264, 294, 342, 352, 354, 364, 366, 370, 378, 396, 408
Offset: 1

Views

Author

Dmitry Petukhov, Oct 04 2015

Keywords

Examples

			(3,5) is a twin primes pair, min(7-5, 3-2)=1, therefore a(1)=1.
(5,7) is a twin primes pair, min(11-7, 5-3)=2>1, therefore a(2)=2.
(11,13) is a twin primes pair, min(17-13, 11-7)=4>2, therefore a(3)=4.
		

Crossrefs

Programs

  • PARI
    {m=0; q=5; s=3; t=2; forprime(p=6, 10^9, if((q-s==2) && (min(p-q, s-t)>m), m=min(p-q, s-t); print1(m, ", ") ); t=s; s=q; q=p;)}

Formula

a(n) = d if ( (p(i+1) = p(i)+2) AND (d = min(p(i+2)-p(i+1), p(i)-p(i-1)) > a(n-1)) ), where a(0) = 0, p(k) = prime(k) = A000040(k).

A069472 Smallest twin prime in a sequence of exactly n disjoint twin pairs, sandwiched between non-twins.

Original entry on oeis.org

29, 101, 179, 9419, 909287, 325267931, 678771479, 1107819732821, 170669145704411, 3324648277099157
Offset: 1

Views

Author

Neil Fernandez, Mar 25 2002

Keywords

Examples

			The first sequence of primes containing exactly 1 pair of twins, sandwiched between non-twins, is 29, 31. The first containing exactly 2 disjoint pairs similarly sandwiched is 101, 103, 107, 109. The first containing exactly 3 disjoint pairs similarly sandwiched is 179, 181, 191, 193, 197, 199. So the sequence starts 29, 101, 179.
		

Crossrefs

Extensions

More terms from Lévai Gábor (gablevai(AT)vipmail.hu), Jan 11 2005
Previous Showing 11-15 of 15 results.