A133688 Least odd primitive abundant number with 3^n as a divisor, but not 3^(n+1).

5391411025, 5775, 1575, 945, 81081, 78975, 1468935, 6375105, 436444281, 5356826865, 21873816315, 371922783705, 2241870572475, 158639164165575, 297836412308955, 1429674513582825, 13431279259253115, 100139192108634825

Offset

0,1

Links

Table of n, a(n) for n=0..17.

Example

5391411025=3^0 * 5^2 * 7 * 11 * 13 * 17 * 19 * 23 * 29 least odd abundant number with no factor 3.
5775 = 3^1 * 5^2 * 7 * 11.
1575 = 3^2 * 5^2 * 13.
945 = 3^3 * 5 * 7.
81081 = 3^4 * 7 * 11 * 13.
78975 = 3^5 * 5^2 * 13.
1468935 = 3^6 * 5 * 13 * 31.
6375105 = 3^7 * 5 * 11 * 53.
436444281 = 3^8 * 7 * 13 * 17 * 43.

Prog

(PARI)
isprab(v) = {my(sig = sigma(v)); if (sig < 2*v, return (0)); if (sig == 2*v, return (1)); fordiv (v, d, if ((d != v) && (sigma(d)>=2*d), return (0)); ); return (1); }
a(n) = {my(p = 3^n, k = 1); while (1, if (k % 3 != 0, v = p * k; if (isprab(v), return (v)); ); k += 2; ); }
\\ Michel Marcus, Mar 07 2013

Crossrefs

Cf. A006038 (odd primitive abundant numbers).

Cf. A115414 (odd abundant numbers not divisible by 3).

Sequence in context: A017529 A321497 A335084 * A306497 A115414 A358412

Adjacent sequences: A133685 A133686 A133687 * A133689 A133690 A133691

Keyword

nonn,more

Author

Pierre CAMI, Jan 04 2008

Extensions

Some terms corrected and a(9)-a(13) from Michel Marcus, Mar 07 2013

a(14)-a(17) from David A. Corneth, Oct 26 2024

Status

approved