A128669 - OEIS

The OEIS is supported by the many generous donors to the OEIS Foundation.

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

Other ways to Give

A128669

Primes p such that p^2 divides 23^(p-1) - 1.

17

13, 2481757, 13703077, 15546404183, 2549536629329

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

COMMENTS

No further terms up to 3.127*10^13.

LINKS

Table of n, a(n) for n=1..5.

Amir Akbary and Sahar Siavashi, The Largest Known Wieferich Numbers, INTEGERS, 18(2018), A3. See Table 1 p. 5.

Richard Fischer, Fermat quotients B^(P-1) == 1 (mod P^2)

MATHEMATICA

Select[Prime[Range[5*10^7]], Mod[ 23^(# - 1) - 1, #^2] == 0 &] (* G. C. Greubel, Jan 18 2018 *)

Select[Prime[Range[93*10^9]], PowerMod[23, #-1, #^2]==1&] (* Harvey P. Dale, May 15 2018 *)

CROSSREFS

Cf. A001220, A014127, A123692, A123693, A128667, A128668, A090968, A039951

Sequence in context: A055324 A228538 A055313 * A013866 A014384 A185213

Adjacent sequences: A128666 A128667 A128668 * A128670 A128671 A128672

KEYWORD

hard,more,nonn

AUTHOR

Alexander Adamchuk, Mar 26 2007

STATUS

approved

NODES