OFFSET

1,2

COMMENTS

Primes 5, 11, 17, 23, 29, 47, 59,... do not appear as largest factors. However, they can be smaller factors. For instance, 4^3 + 1 = 5 * 13.

EXAMPLE

Irregular triangle:

2: {1},

3: {2},

5: {},

7: {3, 5, 19},

11: {},

13: {4, 10, 17, 23},

17: {},

19: {8, 12, 31, 69},

23: {},

29: {},

31: {6, 26, 68},

37: {11, 27, 101},

41: {122},

43: {7, 37, 50, 80, 179},

47: {},

53: {582},

59: {},

61: {14, 48, 75, 563, 719, 2820, 4135},

67: {30, 38, 164, 231, 440, 566, 901, 11093, 112925, 267167},

71: {212},

73: {9, 65, 374, 20303},

79: {24, 56, 103, 293, 530, 656, 767, 868},

83: {82, 2157}.

MATHEMATICA

t = Table[FactorInteger[n^3 + 1][[-1, 1]], {n, 10^6}]; Table[Flatten[Position[t, Prime[n]]], {n, 25}]

CROSSREFS

KEYWORD

nonn,tabf

AUTHOR

T. D. Noe, Apr 03 2013

STATUS

approved