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A335325
Primes p such that d(p^2-1) sets a record, where d(n) is the number of divisors of n.
2
2, 3, 5, 7, 11, 17, 19, 29, 41, 71, 109, 181, 379, 449, 701, 881, 1429, 1871, 2729, 3079, 4159, 5851, 11969, 22679, 23561, 23869, 40699, 65449, 90271, 104651, 188189, 226799, 244529, 252449, 388961, 403649, 815671, 825551, 1276001, 2380951, 2408561
OFFSET
1,1
LINKS
EXAMPLE
7^2-1 = 48 has 10 factors, which is the largest for any prime <= 7 (5^2-1 has 8 factors, 3^2-1 has 4 factors, and 2^2-1 has 2 factors).
MATHEMATICA
seq[len_] := Module[{s = {}, p = 2, dm = 0, c = 0, d}, While[c < len, If[(d = DivisorSigma[0, p^2 - 1]) > dm, dm = d; c++; AppendTo[s, p]]; p = NextPrime[p]]; s]; seq[30] (* Amiram Eldar, Jul 07 2022 *)
PROG
(PARI) my(r=0, d); forprime(p=2, 3*10^6, if((d=numdiv(p^2-1))>r, r=d; print1(p, ", "))); \\ Joerg Arndt, Jun 01 2020
CROSSREFS
Sequence in context: A258261 A228424 A347192 * A189828 A090481 A094342
KEYWORD
nonn
AUTHOR
Austin Nguyen Tran, May 31 2020
STATUS
approved