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 1-6 of 6 results.

A086916 Number of digits in terms of A087732.

Original entry on oeis.org

1, 1, 2, 2, 2, 2, 3, 3, 3, 4, 4, 4, 5, 5, 6, 6, 6, 6, 6, 6, 7, 7, 9, 9, 10, 10, 10, 10, 10, 10, 12, 13, 14, 15, 18, 20, 21, 23, 23, 23, 25, 28, 28, 29, 29, 32, 33, 35, 37, 38, 39, 41, 43, 45, 47, 50, 55, 57, 62, 62, 66, 73, 79, 92, 101, 106, 108, 115, 121, 123, 126, 131, 140, 141
Offset: 1

Views

Author

Pierre CAMI, Sep 25 2003

Keywords

Comments

Number of digits of the twin primes of the form j*P(i)# - 1 and j*P(i)# + 1 with 0 < j < P(i+1), P(i)= i rank primes, P(i)# = primorial of P(i) (A002110).

Examples

			a(23)=9 since A087732(23)=106696589 has 9 digits.
a(31)=12 since A087732(31)=103515091679 has 12 digits.

Crossrefs

Cf. A086916, A087651, A087730, A087731, A087732, A088676.

Extensions

Edited by Ray Chandler, Oct 05 2003

A087832 Numbers k such that k*primorial(2473)-1 is prime.

Original entry on oeis.org

131, 167, 215, 252, 393, 559, 616, 646, 819, 860, 875, 888, 1323, 1364, 1393, 1435, 1523, 1598, 1669, 1734, 1891, 1924, 1951, 2236, 2576, 2761, 2848, 2887, 3138, 3221, 4455, 4540, 4592, 4812, 4818, 5002, 5165, 5188, 5227, 5237, 5306, 5314, 5453, 5540, 5621, 5702
Offset: 1

Views

Author

Pierre CAMI, Oct 07 2003

Keywords

Comments

The "2473" sequence has rather many terms below 2473.

Crossrefs

Cf. A002110, A087730, A087832.

Programs

  • PARI
    N=prod(n=1,366,prime(n));for(k=1,1e5,if(ispseudoprime(k*N-1),print1(k", "))) \\ Charles R Greathouse IV, Dec 28 2011

Formula

a(n) ~ c * n log n with c = 0.07162.... [Charles R Greathouse IV, Dec 28 2011]

Extensions

Edited by Don Reble, Nov 09 2005
a(25)-a(46) from Charles R Greathouse IV, Dec 28 2011

A087651 Sequence of primorials P# (cf. A002110) such that j*P# has twin prime neighbors for some j with 0 < j < prime following P.

Original entry on oeis.org

2, 6, 6, 6, 30, 30, 30, 30, 210, 210, 2310, 2310, 2310, 2310, 30030, 30030, 30030, 30030, 30030, 30030, 510510, 510510, 9699690, 223092870, 223092870, 223092870, 223092870, 223092870, 223092870, 223092870, 6469693230, 200560490130
Offset: 0

Views

Author

Pierre CAMI, Sep 28 2003

Keywords

Comments

I think I have found a proof that the sequence is infinite.

Examples

			I have found the first 122 values of this sequence, 121 and 122 are 2557#, 2557# with j=303 and j=2307, 1087 and 1088 digits.

Crossrefs

The j values are in A087730, P values are in A087731, i values are in A088676.
Cf. A002110, A086916, A087732.
Smaller of twin primes are in A087732. Number of digits in twin primes are in A086916.

Extensions

Edited by Jud McCranie and Ray Chandler, Oct 05 2003

A087833 a(n)*primorial(2423)+1 is prime.

Original entry on oeis.org

211, 252, 372, 414, 416, 498, 533, 576, 724, 738, 793, 832, 1054, 1187, 1344, 1598, 1795, 1946, 2006, 2040, 2051, 2098, 2177, 2283, 2295
Offset: 0

Views

Author

Pierre CAMI, Oct 07 2003

Keywords

Comments

The "2423" sequence has rather many terms below 2423.

Crossrefs

Cf. A002110, A087730-2, A087832, 3, 5, 7.

Extensions

Edited by Don Reble, Nov 09 2005

A087835 a(n)*primorial(2777)-1 is prime.

Original entry on oeis.org

341, 1065, 1559, 1735, 2610
Offset: 0

Views

Author

Pierre CAMI, Oct 07 2003

Keywords

Comments

The "2777" sequence has rather few small terms.

Crossrefs

Cf. A002110, A087730-2, A087832, 3, 5, 7.

Extensions

Edited by Don Reble, Nov 09 2005

A087837 a(n)*primorial(2749)+1 is prime.

Original entry on oeis.org

1017, 1074, 1269, 1771, 2145, 2255
Offset: 0

Views

Author

Pierre CAMI, Oct 07 2003

Keywords

Comments

The "2749" sequence has rather few small terms.

Crossrefs

Cf. A002110, A087730-2, A087832, 3, 5, 7.

Extensions

Edited by Don Reble, Nov 09 2005
Showing 1-6 of 6 results.

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