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.

A231575 Indices of primes in A001590.

Original entry on oeis.org

4, 5, 7, 9, 25, 29, 49, 79, 1613, 15205
Offset: 1

Views

Author

Robert Price, Nov 18 2013

Keywords

Comments

a(11) > 2*10^5.

Crossrefs

Cf. A001590, A231574, A000213, A056816, A157611.

Programs

  • PARI
    v=[1,0,1]; for(n=4,1e4, if(ispseudoprime(t=v[1]+v[2]+v[3]), print1(n", ")); v=[v[2],v[3],t]) \\ Charles R Greathouse IV, Nov 18 2013

Formula

A001590(a(n)) = A231574(n). - Arthur O'Dwyer, 24 Jul 2024

Extensions

Name clarified by Arthur O'Dwyer, Jul 24 2024

A231574 Primes in A001590.

Original entry on oeis.org

2, 3, 11, 37, 634061, 7256527, 1424681173049, 123937002926372177911
Offset: 1

Views

Author

Robert Price, Nov 18 2013

Keywords

Comments

a(9) contains 427 digits and is too large to include here.
a(10) contains 4024 digits and is too large to include here.

Crossrefs

Cf. A000213, A001590, A056816, A157611, A231575.

Extensions

Name clarified by Arthur O'Dwyer, Jul 24 2024

A056816 Primes in the tribonacci sequence A000213.

Original entry on oeis.org

3, 5, 17, 31, 193, 653, 1201, 46499, 532159, 3311233, 128199521, 20512526282340991, 6036724301884645488192191, 2170304813579195568101904406358277391153
Offset: 1

Views

Author

Harvey P. Dale, Sep 01 2000

Keywords

Comments

Primes within A000213.

Crossrefs

Cf. A092836.

Formula

a(n) = A000213(A157611(n)). - R. J. Mathar, Dec 14 2011

A156761 Tribonacci primes that are also primes when their digits are reversed.

Original entry on oeis.org

3, 5, 17, 31, 1201, 128199521
Offset: 1

Views

Author

Jonathan Vos Post, Feb 15 2009

Keywords

Comments

This is to A115347 as Fibonacci numbers A000045 are to A000213 tribonacci numbers. Except for palidromatic tribonacci numbers {3, 5, ...} these are tribonacci emirps, A000213 INTERSECTION A006567.
a(7), if it exists, is greater than A000213(10000). - Dmitry Kamenetsky, Mar 03 2009
a(7), if it exists, is greater than A000213(116404), testing tribonacci primes using A157611. - Michael S. Branicky, May 27 2025

Examples

			a(5) = 1201 because 1201 is prime, and is the 13th tribonacci number A000213(13), and R(1201) = A004086(1201) = 1021 is also prime. a(6) = 128199521 = the 10th tribonacci prime A056816(10), and its digital reverse 125991821 is also prime.

Crossrefs

Cf. A000040, A000045, A000213, A004086, A006567, A056816, A115347, A157611.

Programs

  • Mathematica
    Select[LinearRecurrence[{1,1,1},{1,1,1},200],AllTrue[{#,IntegerReverse[ #]},PrimeQ]&] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Jul 31 2019 *)

Formula

{p such that p is in A000040 and p is in A000213 and R(p) = A004086(p) is in A000040} = {p such that p is in A056816 and R(p) = is in A000040}.
Showing 1-4 of 4 results.

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

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