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A344473
Numbers of the form (q1^b1)(q2^b2)(q3^b3)(q4^b4)(q5^b5)... where q1=7, q2=13, q3=19, q4=31, q5=37, ... (A002476) and b1>=b2>=b3>=b4>=b5...
4
1, 7, 49, 91, 343, 637, 1729, 2401, 4459, 8281, 12103, 16807, 31213, 53599, 57967, 84721, 117649, 157339, 218491, 375193, 405769, 593047, 753571, 823543, 1101373, 1529437, 1983163, 2626351, 2840383, 2989441, 4151329, 4877509, 5274997, 5764801, 7709611
OFFSET
1,2
COMMENTS
A343771 is a subsequence.
LINKS
EXAMPLE
12103 is a term since 12103 = 7^2 * 13 * 19.
22477 is not a term since 22477 = 7 * 13^2 * 19, the exponents are not nonincreasing.
PROG
(PARI) \\ following program for A054994
list_A344473(lim) =
{
my(u = [1], v = List(), w = v, pr, t = 1);
forprime(p = 7, ,
if (p % 3 > 1, next);
t *= p;
if (t > lim,
break);
listput(w, t)
);
for (i = 1, #w,
pr = 1;
for (e = 1, logint(lim\ = 1, w[i]),
pr *= w[i];
for (j = 1, #u,
t = pr * u[j];
if (t > lim,
break);
listput(v, t)
)
);
if (w[i] ^ 2 < lim, u = Set(concat(Vec(v), u)); v = List());
);
Set(concat(Vec(v), u));
}
list_A344473(100000)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Jianing Song, May 20 2021
STATUS
approved