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

Author

Miles Englezou, Jun 04 2025

Keywords

• nonn

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.

Examples

			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.
		

Crossrefs

Cf. A024934, A383844.

Programs

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))