A278250 Least number with the prime signature of the n-th Wedderburn-Etherington number (A001190).

1, 1, 1, 2, 2, 6, 2, 2, 6, 12, 12, 6, 2, 2, 60, 30, 2, 6, 120, 6, 6, 180, 2, 12, 30, 210, 6, 2, 2, 30, 210, 6, 30, 900900, 30, 180, 24, 210, 60060, 210, 13860, 120, 210, 210, 210, 96, 30, 60060, 6126120, 2310, 30, 60, 2310, 2310, 30, 4620, 210, 240, 210, 120, 30, 60, 2, 1260, 30, 30, 2310, 2310, 60, 18480, 30, 2310, 420, 30, 2310, 18480, 30, 3360, 210, 2, 420, 30

Offset: 1

Author

Antti Karttunen, Nov 22 2016

Keywords

• nonn

Links

• Antti Karttunen, Table of n, a(n) for n = 1..213

Crossrefs

Cf. A001190, A046523.

Cf. also A278258.

Programs

PARI

{A001190(n) = local(A); if( n<4, n>0, A = vector(n, i, 1); for( i=4, n, A[i] = sum( j=1, (i-1)\2, A[j] * A[i-j]) + if( i%2, 0, A[i/2] * (A[i/2] + 1)/2)); A[n])}; /* Michael Somos, Mar 25 2006 */
A046523(n) = my(f=vecsort(factor(n)[, 2], , 4), p); prod(i=1, #f, (p=nextprime(p+1))^f[i]) \\ Charles R Greathouse IV, Aug 17 2011
A278250(n) = A046523(A001190(n));
for(n=1, 213, write("b278250.txt", n, " ", A278250(n)));

Scheme

(define (A278250 n) (A046523 (A001190 n)))

Formula

a(n) = A046523(A001190(n)).