A180471 Irregular triangle in which row n has all primes q such that prime(n)*q is a base-2 Fermat pseudoprime.

31, 257, 73, 89, 683, 113, 11, 151, 331, 73, 109, 61681, 127, 337, 5419, 178481, 2796203, 157, 1613, 233, 1103, 2089, 3033169, 1321, 20857, 599479, 281, 86171, 122921, 19, 37, 109, 433, 38737, 2731, 8191, 121369, 22366891, 13367, 164511353, 8831418697, 23, 353, 397, 683, 2113, 2931542417

Offset: 5

Author

T. D. Noe, Jan 19 2011

Keywords

• nonn
• tabf

Comments

The length of row n is A085014(n). The smallest and largest primes in row n are A085012(n) and A085019(n).

Examples

			The irregular triangle begins
31
none
257
73
89, 683
113
11, 151, 331
73, 109
61681
		

References

• See A085012.

Links

• Amiram Eldar, Table of n, a(n) for n = 5..3424
• Index entries for sequences related to pseudoprimes

Crossrefs

Cf. A085012, A085014, A085019.

Programs

Mathematica

Flatten[Table[p=Prime[n]; q=Transpose[FactorInteger[2^(p-1)-1]][[1]]; cnt={}; Do[If[PowerMod[2, p*q[[i]]-1, p*q[[i]]]==1, AppendTo[cnt,q[[i]]]], {i,Length[q]}]; cnt, {n,5,50}]]