A226959 a(0)=1 and a(n)=prime(n)*lcm(prime(n)-1, a(n-1)) for n > 0.

1, 2, 6, 60, 420, 4620, 60060, 4084080, 232792560, 5354228880, 155272637520, 4813451763120, 178097715235440, 7302006324653040, 313986271960080720, 14757354782123793840, 782139803452561073520, 46146248403701103337680, 2814921152625767303598480

Offset

0,2

Comments

A226957(a(n)) = n.

Is this a subset of A168264? - Ralf Stephan, Jul 04 2013

Links

Charles R Greathouse IV, Table of n, a(n) for n = 0..347

Mathematica

a[0]=1; a[n_]:= a[n]=Prime[n]*LCM[a[n - 1], Prime[n] -1];
Table[a[i], {i, 1, 18}]

Prog

(PARI) a(n)=if(n, my(v=primes(n), e=vector(n, i, 1), f, j); forprime(p=2, v[n], f=factor(p-1); for(i=1, #f~, if(f[i, 2]>1, j=primepi(f[i, 1]); e[j]=max(e[j], f[i, 2])))); prod(i=1, n, v[i]^e[i]), 1) \\ Charles R Greathouse IV, Jun 28 2013

Crossrefs

Cf. A226957, A002110.

Sequence in context: A102290 A025540 A334224 * A083135 A056604 A376515

Adjacent sequences: A226956 A226957 A226958 * A226960 A226961 A226962

Keyword

nonn

Author

José María Grau Ribas, Jun 24 2013

Status

approved