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A354922 Positions of even terms in A182665. 3

%I #15 Jun 17 2022 16:06:12

%S 1,6,10,14,15,18,20,22,24,26,33,34,36,38,42,45,46,50,51,52,54,58,62,

%T 63,65,68,69,70,72,74,77,78,82,84,86,87,88,91,94,95,96,98,100,106,110,

%U 112,114,115,116,118,122,123,134,136,140,141,142,143,145,146,148,150,152,153,156,158,159,160,161,162,164,166

%N Positions of even terms in A182665.

%C Numbers k such that the parity of A344005(k) is the same as the parity of k itself, or in other words, numbers k for which A354918(k) = A000035(k).

%o (PARI)

%o A354920(n) = forstep(x=n-1,0,-1,if(!((x*(x-1))%n),return(x%2)));

%o isA354922(n) = !A354920(n);

%o (Python 3.8+)

%o from itertools import combinations, islice, count

%o from math import prod

%o from sympy import factorint

%o from sympy.ntheory.modular import crt

%o def A354922_gen(startvalue=1): # generator of terms >= startvalue

%o if startvalue <= 1:

%o yield 1

%o for n in count(max(startvalue,2)):

%o plist = tuple(p**q for p, q in factorint(n).items())

%o if len(plist) != 1 and not (n-int(min(min(crt((m, n//m), (0, -1))[0], crt((n//m, m), (0, -1))[0]) for m in (prod(d) for l in range(1, len(plist)//2+1) for d in combinations(plist, l))))) & 1:

%o yield n

%o A354922_list = list(islice(A354922_gen(),40)) # _Chai Wah Wu_, Jun 12 2022

%Y Positions of zeros in A354920.

%Y Cf. A000035, A182665, A344005, A354918, A354921 (complement).

%K nonn

%O 1,2

%A _Antti Karttunen_, Jun 12 2022

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Last modified July 14 02:38 EDT 2024. Contains 374291 sequences. (Running on oeis4.)