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August 27, 2015
Posted by **Chris** on Monday, May 7, 2012 at 8:07am.

- math -
**Steve**, Monday, May 7, 2012 at 10:23amabcdef

a=b+4

c=f-1

de=af

Let's see what de can be, and what af could then be. Remember that a>=5, since b>=1

de: af

14: 72 b=3 c=1 no

15: 53 no, odd

16: 82 b=3 c=1 no

18: 92 b=5 c=1 no, or 63 b=2 c=1 no

21: 73 no, odd

24: 83 no, odd

27: 93 no, odd

28: 74 b=3 c=3 no

32: 84 b=4 no

36: 94 b=5 c=3 no

42: 67 no, odd; 76 b=3 c=5 YES

54: 69 no, odd; or 96 b=5 no

56: 78 b=3 c=7 no, or 87 b=4 c=6 no

63: 79 or 97 no, both odd

72: 89 no, odd; 98 b=5,c=7 no

So, we are left with 735426