A357280 Smallest m such that m^k-2 and m^k+2 are prime for k=1..n.

5, 9, 102795, 559838181, 27336417022509

Offset

1,1

Links

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

Example

a(3) = 102795 because:
for k = 1; 102795^1-2 = 102793 and 102795^1+2 = 102797, both of which are prime, and
for k = 2; 102795^2-2 = 10566812023 and 102795^2+2 = 10566812027, both of which are prime, and
for k = 3; 102795^3-2 = 1086215442109873 and 102795^3+2 = 1086215442109877, both of which are prime, and
102795 is the smallest number with this property.

Prog

(PARI) isok(m, n) = for (k=1, n, if(!isprime(m^k-2) || !isprime(m^k+2), return(0)); ); return(1);
a(n) = my(m=1); while(!isok(m, n), m++); m; \\ Michel Marcus, Nov 14 2022

Crossrefs

Cf. A189051, A245510, A245512, A329727.

Sequence in context: A348132 A098135 A112259 * A370131 A258150 A330599

Adjacent sequences: A357277 A357278 A357279 * A357281 A357282 A357283

Keyword

nonn,more,hard

Author

Kellen Shenton, Sep 24 2022

Status

approved