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

1,1

Links

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

Example

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

Prog

(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

Crossrefs

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

Sequence in context: A017506 A017638 A221557 * A159301 A113027 A094722

Adjacent sequences: A217000 A217001 A217002 * A217004 A217005 A217006

Keyword

nonn

Author

Donovan Johnson, Sep 22 2012

Status

approved