A345056 a(n) is the next larger number k > n for which A011772(k) = A011772(n), or n itself if no such larger number exists.

1, 6, 3, 14, 10, 6, 21, 20, 12, 10, 55, 18, 26, 28, 15, 62, 34, 36, 57, 24, 21, 33, 253, 30, 50, 39, 117, 28, 58, 40, 93, 72, 66, 68, 105, 36, 74, 95, 78, 60, 82, 70, 129, 48, 45, 69, 1081, 88, 56, 75, 153, 130, 106, 63, 55, 84, 171, 203, 1711, 120, 122, 124, 126, 254, 325, 66, 201, 136, 92, 210, 355, 96, 146, 111, 100, 114

Offset

1,2

Links

Table of n, a(n) for n=1..76.

Formula

a(n) = n + A345057(n).

Prog

(PARI)
A011772(n) = { if(n==1, return(1)); my(f=factor(if(n%2, n, 2*n)), step=vecmax(vector(#f~, i, f[i, 1]^f[i, 2]))); forstep(m=step, 2*n, step, if(m*(m-1)/2%n==0, return(m-1)); if(m*(m+1)/2%n==0, return(m))); }; \\ From A011772
A345056(n) = { my(x=A011772(n), y=binomial(x+1, 2)); for(i=1+n, y, if(A011772(i)==x, return(i))); (n); };

Crossrefs

Cf. A000217, A002024, A011772, A066561, A345057, A345058.

Sequence in context: A320038 A214498 A128756 * A049784 A341746 A097917

Adjacent sequences: A345053 A345054 A345055 * A345057 A345058 A345059

Keyword

nonn

Author

Antti Karttunen, Jun 07 2021

Status

approved