A255423 - OEIS

A255423

The least number k > A255334(n) for which A000203(k) = A000203(A255334(n)) and A007947(k) = A007947(A255334(n)), where A000203 gives the sum of divisors, and A007947 gives the squarefree kernel of n.

2058, 10290, 22638, 26754, 34986, 39102, 47334, 51450, 59682, 52728, 63798, 76146, 84378, 88494, 96726, 109074, 113190, 121422, 125538, 133770, 137886, 146118, 150234, 162582, 170814, 174930, 183162, 195510, 199626, 207858, 211974, 220206, 224322, 232554, 236670, 249018, 257250, 261366, 269598, 281946, 286062, 294294

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

OFFSET

1,1

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..6589

FORMULA

a(n) = A255424(n) * A255426(n).

PROG

(PARI)

A007947(n) = factorback(factorint(n)[, 1]);

nextone(n) = { if(!n, return(0)); my(r=A007947(n), s=sigma(n), k=n+r); while(k<s, if((sigma(k) == s)&&(A007947(k) == r), return(k), k = k+r)); return(0); };

i=0; for(n=1, 2^25, k = nextone(n); if(k, i++; write("b255423.txt", i, " ", k))); \\ Andrew Lelechenko, May 09 2014

CROSSREFS

Cf. A000203, A007947, A255334.

Cf. also A255335 (same sequence sorted into ascending order), A255424 (squarefree kernel of a(n)), A255426 (same terms with but with their squarefree kernel divided out of them).

Sequence in context: A252112 A045055 A255335 * A202418 A069427 A357918

Adjacent sequences: A255420 A255421 A255422 * A255424 A255425 A255426

KEYWORD

nonn

AUTHOR

Antti Karttunen, Apr 06 2015

STATUS

approved