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A352797 Let S(k) be the subsequence of multiples of k from k*positive integers where each element of S(k) sets a new record of divisors in that sequence. Then f(k) is the first element from S(k)/k that is not a power of 2. Sequence lists records for f(k). 1
1, 3, 9, 45, 135, 945, 2835, 14175, 155925, 467775, 6081075 (list; graph; refs; listen; history; text; internal format)



Conjecture: Subsequence of A147516.


Table of n, a(n) for n=1..11.


For k=1, the sequence of multiples of 1 that set records for numbers of divisors (divided by 1) starts 1,2,4,6. (A002182)

For k=3, the sequence starts 1,2,4,8,12. (A351623)

For k=9, the sequence starts 1,2,4,8,16,20.

For k=45, the sequence starts 1,2,4,8,16,24.


(PARI) isp2(n) = if (n<=2, return(1)); my(m); ispower(n, , &m) && (m==2);

f(n) = {my(m=1, nm, k=1, ok=0); until(ok, nm = numdiv(k*n); if (nm > m, m = nm; if (!isp2(k), ok = 1); ); if (!ok, k++); ); k; }

lista(nn) = {my(m=1, fm); for (n=1, nn, fm = f(n); if (fm > m, m = fm; print1(n, ", "); ); ); } \\ Michel Marcus, May 05 2022


Cf. A002182, A351623, A147516.

Sequence in context: A209977 A001902 A224085 * A192891 A068100 A327648

Adjacent sequences: A352794 A352795 A352796 * A352798 A352799 A352800




J. Lowell, Apr 03 2022



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Last modified December 7 13:02 EST 2022. Contains 358656 sequences. (Running on oeis4.)