A328249 - OEIS

The OEIS is supported by the many generous donors to the OEIS Foundation.

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

Other ways to Give

A328249

Numbers k such that the third arithmetic derivative of A276086(k) is prime.

5, 15, 21, 31, 43, 79, 91, 98, 104, 106, 223, 229, 231, 254, 255, 289, 291, 301, 305, 423, 453, 456, 487, 670, 674, 677, 692, 702, 730, 736, 2343, 2378, 2380, 2400, 2409, 2534, 2537, 2543, 2552, 2562, 2585, 2602, 2618, 2629, 2767, 2804, 2821, 2831, 2839, 2942, 2943, 2957, 2962, 2963, 2974, 4621, 4669, 4672, 4687, 4717, 4841, 4844

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

OFFSET

1,1

COMMENTS

Numbers k such that A003415(A003415(A327860(k))) = A099306(A276086(k)) is a prime.

Numbers k such that A276086(k) is in A328239.

For all n, A327969(a(n)) <= 6. This is sharp for example with a(7) = 91.

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..1315

PROG

(PARI)

A003415(n) = if(n<=1, 0, my(f=factor(n)); n*sum(i=1, #f~, f[i, 2]/f[i, 1]));

A327860(n) = { my(m=1, i=0, s=0, pr=1, nextpr); while((n>0), i=i+1; nextpr = prime(i)*pr; if((n%nextpr), my(e=((n%nextpr)/pr)); m *= (prime(i)^e); s += (e / prime(i)); n-=(n%nextpr)); pr=nextpr); (s*m); };

isA328249(n) = isprime(A003415(A003415(A327860(n))));

CROSSREFS

Cf. A003415, A099306, A276086, A327860, A327969, A328239, A328233, A328240.

Sequence in context: A345645 A274535 A027184 * A110702 A141394 A127256

Adjacent sequences: A328246 A328247 A328248 * A328250 A328251 A328252

KEYWORD

nonn

AUTHOR

Antti Karttunen, Oct 11 2019

STATUS

approved