A365248 Composite numbers k that are not a prime minus one, for which A214749(k) = k/2.
34, 94, 118, 142, 202, 214, 246, 274, 298, 334, 394, 402, 436, 454, 514, 526, 538, 622, 628, 634, 694, 706, 712, 754, 766, 778, 802, 814, 892, 898, 922, 934, 942, 958, 1002, 1006, 1042, 1054, 1114, 1126, 1132, 1138, 1146, 1158, 1174, 1198, 1234, 1246, 1270
Offset: 1
Keywords
Links
- Chai Wah Wu, Table of n, a(n) for n = 1..10000
Programs
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PARI
f(n) = my(m=1); while((n^2+m) % (n-m), m++); m; \\ A214749 lista(nn) = my(list=List()); forcomposite(c=1, nn, if ((f(c) == c/2) && !isprime(c+1), listput(list, c))); Vec(list); \\ Michel Marcus, Sep 08 2023
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Python
from sympy import isprime a=[] for n in range(2,1000): for m in range(1,n//2+1): if (n**2+m)%(n-m)==0: if m==n/2 and not isprime(n+1): a.append(n) break print(a) -
Python
from itertools import count, islice from sympy import isprime from sympy.abc import x, y from sympy.solvers.diophantine.diophantine import diop_quadratic def A365248_gen(startvalue=2): # generator of terms >= startvalue return filter(lambda n:not isprime(n+1) and min(int(x) for x,y in diop_quadratic(n*(n-y)+x*(y+1)) if x>0)==n>>1, count(max(startvalue+startvalue&1,2),2)) A365248_list = list(islice(A365248_gen(),30)) # Chai Wah Wu, Oct 06 2023
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