A217003 Lucas-Carmichael numbers with 7 prime factors.

3512071871, 10470856319, 11956093919, 12283814015, 13150303199, 15128703359, 15966728855, 18063158399, 21887083295, 22572006479, 23388059519, 23836221695, 23940514367, 25231063319, 25638464159, 27742047839, 28160966735, 30070781279, 31251542399, 35160944399

Offset: 1

Author

Donovan Johnson, Sep 22 2012

Keywords

• nonn

Examples

			A006972(1249) = 3512071871 = 7*11*17*23*31*53*71.
		

Links

• Daniel Suteu, Table of n, a(n) for n = 1..7464 (first 1000 terms from Donovan Johnson)

Crossrefs

Cf. A006972 (Lucas-Carmichael numbers), A216925, A216926, A216927, A217002, A217091.

Programs

PARI

upto(n, k=7) = my(A=vecprod(primes(k+1))\2, B=n); (f(m, l, p, k, u=0, v=0) = my(list=List()); if(k==1, forprime(p=u, v, my(t=m*p); if((t+1)%l == 0 && (t+1)%(p+1) == 0, listput(list, t))), forprime(q = p, sqrtnint(B\m, k), my(t = m*q); my(L=lcm(l, q+1)); if(gcd(L, t) == 1, my(u=ceil(A/t), v=B\t); if(u <= v, my(r=nextprime(q+1)); if(k==2 && r>u, u=r); list=concat(list, f(t, L, r, k-1, u, v)))))); list); vecsort(Vec(f(1, 1, 3, k))); \\ Daniel Suteu, Aug 30 2022