A037025 a(1) = 8; a(n) = least k with d(k) = a(n-1), where d(k) is the number of divisors of k.

8, 24, 360, 3603600, 2549066103582535692163008000000

Offset: 1

Author

Donald S. McDonald

Keywords

• nonn
• nice

Comments

Unless a(5) is an "exceptional" (or "extraordinary") number (see A072066), a(6) = 2^30 * 3^28 * 5^22 * 7^18 * 11^16 * 13^16 * 17^12 * 19^12 * 23^10 * 29^10 * 31^10 * 37^10 * 41^6 * 43^6 * 47^6 * 53^6 * 59^4 * 61^4 * 67^4 * 71^4 * 73^4 * 79^4 * 83^2 * 89^2 * 97^2 * 101^2 * 103^2 * 107^2 * 109^2 * 113^2 * 127^2 * 131^2 * 137 * 139 * 149 * 151 * 157 * 163 * 167 * 173 * 179 * 181 * 191 * 193 = 1.77955...*10^327 (a 328-digit number). - Jon E. Schoenfield, Sep 07 2023

Crossrefs

Cf. A000005, A009287.

Programs

PARI

lista(nn) = {a=8; print1(a, ", "); for (n=2, nn, k=1; while(numdiv(k) != a, k++); print1(k, ", "); a = k;);} \\ Michel Marcus, Feb 17 2015

Extensions

One more term from Naohiro Nomoto, Jun 28 2001