A278250 - OEIS

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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

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,4

LINKS

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

FORMULA

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

PROG

(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)))

CROSSREFS

Cf. A001190, A046523.

Cf. also A278258.

Sequence in context: A352892 A126889 A205030 * A357441 A134339 A162299

Adjacent sequences: A278247 A278248 A278249 * A278251 A278252 A278253

KEYWORD

nonn

AUTHOR

Antti Karttunen, Nov 22 2016

STATUS

approved