login
A332229
Even numbers k such that A156552(k) is not a power of prime, and for which A323243(k) = sigma(A156552(k)) is congruent to 2 modulo 8.
2
290, 434, 550, 826, 858, 1394, 1798, 2254, 2418, 2546, 2950, 3094, 3910, 4150, 4382, 4930, 5590, 6138, 6358, 6390, 6710, 6966, 7514, 7546, 7622, 7658, 7990, 8550, 8798, 8906, 9230
OFFSET
1,1
COMMENTS
Numbers k for which A156552(k) is in A332228.
Sequence A005940(1+A332228(n)), n >= 1, sorted into ascending order.
PROG
(PARI)
A156552(n) = {my(f = factor(n), p2 = 1, res = 0); for(i = 1, #f~, p = 1 << (primepi(f[i, 1]) - 1); res += (p * p2 * (2^(f[i, 2]) - 1)); p2 <<= f[i, 2]); res}; \\ From A156552
isA332228(n) = ((n%2)&&!isprimepower(n)&&2==(sigma(n)%8));
isA332229(n) = isA332228(A156552(n));
(PARI)
v156552sigs = readvec("a156552.txt"); \\ Factorization file for A156552 prepared by Hans Havermann, available at https://oeis.org/A156552/a156552.txt
isA156552not_a_primepower(n) = if(n<=2, 0, my(prsig=v156552sigs[n]); length(prsig[1])>1);
A323243(n) = if(n<=2, n-1, my(prsig=v156552sigs[n], ps=prsig[1], es=prsig[2]); prod(i=1, #ps, ((ps[i]^(1+es[i]))-1)/(ps[i]-1)));
isA332229(n) = (!(n%2)&&isA156552not_a_primepower(n)&&(2==(A323243(n)%8)));
k=0; for(n=1, 10000, if(isA332229(n), k++; print1(n, ", ")));
CROSSREFS
Subsequence of A324814.
Sequence in context: A186553 A075420 A075421 * A296055 A090839 A158255
KEYWORD
nonn
AUTHOR
Antti Karttunen, Feb 13 2020
STATUS
approved