A372564 Positions of -4's in A346242.

72, 260, 380, 620, 740, 860, 1220, 1340, 1460, 1580, 1940, 2060, 2180, 2540, 2780, 3020, 3140, 3260, 3620, 3860, 3980, 4220, 4460, 4580, 4820, 5420, 5540, 5660, 6140, 6260, 6620, 6740, 6980, 7340, 7460, 7580, 7940, 8180, 8420, 8660, 8780, 9140, 9260, 9740, 9980, 10460, 10820, 10940, 11420, 11540, 12020, 12140, 12260

Offset: 1

Author

Antti Karttunen, May 24 2024

Keywords

• nonn

Comments

Term a(94)=23256 is the first term after 72 that is not a multiple of 20. The first four odd terms 71825, 942667, 1322035, 3613027 occur at indices n=273, 3355, 4619, 11995.

Of the first 20000 terms, 13422 are multiples of 20, and apparently, for any n > 1, 20*A002476(n) is included in this sequence.

Links

• Antti Karttunen, Table of n, a(n) for n = 1..20000
• Index entries for sequences related to primorial base

Crossrefs

Cf. A002476, A346242.

Cf. also A354814.

Programs

PARI

A324198(n) = { my(m=1, p=2, orgn=n); while(n, m *= (p^min(n%p, valuation(orgn, p))); n = n\p; p = nextprime(1+p)); (m); };
memoA346242 = Map();
A346242(n) = if(1==n,1,my(v); if(mapisdefined(memoA346242,n,&v), v, v = -sumdiv(n,d,if(dA324198(n/d)*A346242(d),0)); mapput(memoA346242,n,v); (v)));
isA372564(n) = (-4==A346242(n));