A384310 Numbers k such that A383844(k) and A383844(k+1) are nonzero.

0, 3, 6, 7, 12, 20, 26, 27, 28, 53, 56, 61, 74, 88, 145, 146, 252, 289, 299, 308, 320, 323, 340, 471, 577, 578, 739, 1240, 1517, 1568, 1579, 1857, 2638, 3042, 3043, 3133, 3455, 3565, 4910, 8683, 8684, 8857, 8858, 9291, 14549, 17913, 18117, 20005, 21989, 32552, 37902, 42514, 44869, 47877, 49942

Offset

1,2

Comments

a(n) is the lesser term of a pair of consecutive nonzero terms in A383844.

Triplets of consecutive nonzero terms can also be found in A383844 and are represented here as pairs. Up to n = 83354 there are 8 such triplets, the least terms of each being 6, 26, 27, 145, 577, 3042, 8683, 8857.

Links

Table of n, a(n) for n=1..55.

Example

26 is a term since A383844(26) and A383844(27) are nonzero.
27 is a term since A383844(27) and A383844(28) are nonzero.
252 is a term since A383844(252) and A383844(253) are nonzero.
61890 is a term since A383844(61890) and A383844(61891) are nonzero.

Prog

(PARI) isok(n) = (count(n) = my(f, S=[], b); (f(m)=my(r=0); forprime(p=2, m, r+=m%p); return(r)); if(n<=21, b=26); if(n>21, b=n); if(n>=250, b=n^0.8); if(n>=6000, b=n^0.7); if(n>=21000, b=n^0.68); if(n>=43000, b=n^0.67); for(k=0, b, if(f(k)==n, S=concat(S, k))); return(S)); if(n==0 || (n>1 && count(n)<>[] && count(n+1)<>[]), return(1), return(0))

Crossrefs

Cf. A024934, A383844.

Sequence in context: A370900 A069891 A190118 * A249714 A250177 A333002

Adjacent sequences: A384307 A384308 A384309 * A384311 A384312 A384313

Keyword

nonn

Author

Miles Englezou, Jun 04 2025

Status

approved