A230668 -id:A230668 - cp's OEIS frontend

A230715 Smallest numbers in a set of 4 consecutive odd numbers that are primes or pseudoprime (base 2).

641, 656597, 6212357, 18958567877, 287468425241, 626160901277, 634038307447, 1395494019917, 1925525109197, 1960708164797, 1962378065897, 1977370759361, 2788325761547, 3032013857177, 4846359321103, 6877227801077, 11927878640383, 20835183400303, 22298617759877

Offset: 1

Shyam Sunder Gupta, Oct 28 2013

nonn

			656597 is in sequence because 656597, 656599, 656601, 656603 is a set of 4 consecutive odd number where 656601 is pseudoprime base 2 and others are prime.

Shyam Sunder Gupta, Table of n, a(n) for n = 1..913
Jan Feitsma, Tables of pseudoprimes and related data

Cf. A001567, A230559, A228575, A230668.

\\ Import A001567 into the vector v
for(i=1,#v, start=stop=v[i]; while(ok(start-=2),); while(ok(stop+=2),); while(stop-start>9, print1(start+=2, ", "))) \\ Charles R Greathouse IV, Oct 28 2013

A228455 Pseudoprimes n to base 2 such that n-2, n+2, n-4 and n+4 are primes.

Original entry on oeis.org

280743771536011785, 666787209284980785, 1386744766793550165, 6558237049521329745, 11646802313400102465

Offset: 1

Shyam Sunder Gupta, Oct 27 2013

All numbers in this sequence end in 5 because n-4 , n-2 is a twin prime pair and so also is n+2 and n+4.

For all n, a(n) - 4 is in A230668(n). Somewhat surprisingly, all terms of A230668 known so far are of that form. - M. F. Hasler, Dec 08 2016

			280743771536011785 is a pseudoprime (base 2) and 280743771536011781, 280743771536011783, 280743771536011787 and 280743771536011789 are primes.

Cf. A001567, A057942, A230488, A230489.

A230808 Smallest sets of 3 consecutive odd numbers that are primes or pseudoprime (base 2). The initial odd number is listed.

Original entry on oeis.org

3, 641, 643, 4369, 25759, 33149, 87249, 129917, 157637, 212419, 332947, 451901, 656597, 656599, 831405, 1489665, 1608461, 2113665, 3020357, 3370637, 6212357, 6212359, 19092917, 31880577, 34487597, 38790749, 63560683, 81612105, 84028407, 86559045, 274014885

Offset: 1

Shyam Sunder Gupta, Oct 30 2013

nonn

			641 is in sequence because 641, 643, 645 is a set of 3 consecutive odd number where 645 is pseudoprime base 2 and others are prime.

Shyam Sunder Gupta, Table of n, a(n) for n = 1..5001
Jan Feitsma, Tables of pseudoprimes and related data

Cf. A001567, A230559, A228575, A230668, A230715.

cp's OEIS Frontend

A230715 Smallest numbers in a set of 4 consecutive odd numbers that are primes or pseudoprime (base 2).

Views

Author

Keywords

Examples

Links

Crossrefs

Programs

PARI

A228455 Pseudoprimes n to base 2 such that n-2, n+2, n-4 and n+4 are primes.

Views

Author

Keywords

Comments

Examples

Crossrefs

A230808 Smallest sets of 3 consecutive odd numbers that are primes or pseudoprime (base 2). The initial odd number is listed.

Views

Author

Keywords

Examples

Links

Crossrefs