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A175345
Numbers m such that A006218(m) is a perfect square.
2
1, 7, 101, 312, 351, 448, 479, 726, 781, 897, 1040, 1580, 1605, 2159, 2339, 2783, 3298, 3739, 4485, 4608, 4650, 4735, 4776, 4902, 5473, 6746, 6894, 6994, 8353, 8961, 10117, 10658, 11714, 12226, 13758, 14309, 14729, 15512, 18446, 18682
OFFSET
1,2
LINKS
Chai Wah Wu, Table of n, a(n) for n = 1..10000 (terms 1..286 from Robert Israel)
EXAMPLE
If A027750 is displayed as a triangle where the row lengths are successive odd integers:
1; <-- 1
1, 2; 1,
3; 1, 2, 4; 1,
5; 1, 2, 3, 6; 1, 7: <-- 7
1, 2, 4, 8; 1, 3, 9; 1, 2,
...
MAPLE
N:= 10^5: # to get all entries up to N
A:= Vector(N, numtheory:-tau, datatype=integer[8]):
C:= Statistics:-CumulativeSum(A);
select(t -> issqr(round(C[t])), [$1..N]); # Robert Israel, May 19 2014
PROG
(PARI) lista(nn) = {s = 0; for (n=1, nn, s += numdiv(n); if (issquare(s), print1(n, ", ")); ); } \\ Michel Marcus, Oct 19 2015
(Python)
from sympy import integer_nthroot, divisor_count
A175345_list, k, c, = [], 1, 1
while k < 10**4:
if integer_nthroot(c, 2)[1]: A175345_list.append(k)
k += 1
c += divisor_count(k) # Chai Wah Wu, Oct 11 2021
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Ctibor O. Zizka, Apr 17 2010
STATUS
approved