A308242 Odd numbers k such that A(k) == 0 (mod k) (see Comments for details).

525, 705, 1725, 25935, 50325, 61755, 72345, 231735, 436821, 473109, 1188525, 2308911, 3353025, 4876437, 4953165, 5928285, 7739985, 8019375, 8224125, 18163299, 24088155, 28393365, 32717685, 40981125, 46830225, 89995191, 104334465, 124061925, 150079215, 177190275

Offset

1,1

Comments

For the definition of A(k), see Cosgrave, Dilcher, 2013, (3.2).

The values of a(1)-a(26) are given in Cosgrave, Dilcher, 2013, table 1.

Links

Table of n, a(n) for n=1..30.

John B. Cosgrave and Karl Dilcher, On a congruence of Emma Lehmer related to Euler numbers, Acta Arithmetica 161 (2013), 47-67; see also.

Prog

(PARI) is(k) = my(f=factor(k), p, q, r=#f~, s, t); if(r>2 && f[1, 1]==3 && f[1, 2]==1 && sum(i=2, r, f[i, 1]%4==1), for(i=2, r, p=f[i, 1]; s=Mod(9, p^(f[i, 2]+2)); t=Mod(10*p^2, p^(f[i, 2]+2)); for(j=2, r, q=f[j, 1]; s*=q^(2*f[j, 2])*(q=q^2-(-1)^(q\2)); if(i!=j, t*=q)); if(s+t, return(0))); 1, 0); \\ Jinyuan Wang, Sep 08 2025

Crossrefs

Sequence in context: A381619 A125012 A281549 * A260606 A181112 A152464

Adjacent sequences: A308239 A308240 A308241 * A308243 A308244 A308245

Keyword

nonn

Author

Felix Fröhlich, May 16 2019

Extensions

a(27)-a(30) from Jinyuan Wang, Sep 08 2025

Status

approved