A262748
Composite odd numbers m such that q is not equal to -1 (mod p) for every pair p,q
9, 21, 25, 27, 35, 39, 49, 55, 57, 77, 81, 85, 93, 111, 115, 117, 119, 121, 125, 129, 133, 143, 155, 161, 169, 171, 183, 185, 187, 201, 203, 205, 209, 215, 217, 219, 235, 237, 243, 247, 253, 259, 265, 275, 279, 289, 291, 299, 301, 305, 309, 319, 323, 327, 329, 333
Offset: 1
Keywords
Links
- Serafín Ruiz-Cabello, On the use of the lowest common multiple to build a prime-generating recurrence, arXiv:1504.05041 [math.CO], 2015.
Programs
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Sage
def triangle(q, m): # This is the first auxiliary program if q >= m: return False Q = factor(q) for par in Q: if m % par[0] != 0: return False return True def pairs(m): # This is the second auxiliary program L = [] M = factor(m) for par in M: p = par[0] for q in range(p-1,m,p): if triangle(q, m): L.append((p, q)) return L def print_presents(n0, n): # This program gives a list with every present number in the interval [n0, n] L = [] m0 = n0+1-(n0%2) for m in range(m0,n+1,2): if not is_prime(m): if pairs(m) == []: L.append(m) return L # Serafín Ruiz-Cabello, Sep 30 2015
Comments