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Search: id:A121058
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| A121058 |
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Positive integers x such that x+d+1 is composite for all divisors d of x. |
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1
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| 7, 13, 19, 22, 31, 37, 42, 43, 46, 47, 49, 61, 62, 67, 73, 79, 82, 91, 97, 103, 109, 118, 121, 122, 126, 127, 133, 139, 142, 151, 157, 163, 166, 167, 169, 172, 181, 193, 199, 202, 206, 211, 212, 213, 214, 217, 218, 223, 229, 241, 242, 246, 247, 250, 256, 257
(list; graph; listen)
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OFFSET
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1,1
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LINKS
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D Numbers.
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FORMULA
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a(n)=nth number x such that x+d+1 is composite for all divisors d of x.
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EXAMPLE
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a(9)=46=2*23 since 46+1+1=48=16*3, 46+2+1=49=7*7, 46+23+1=70=2*5*7, 46+46+1=93=3*31.
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MAPLE
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with(numtheory): cnt:=0: L:=[]: for w to 1 do for n from 1 while cnt<100 do dn:=divisors(n); Q:=map(z-> n+z+1, dn); if andmap(z-> not isprime(z), Q) then cnt:=cnt+1; L:=[op(L), [cnt, n]]; fi; od od; L;
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CROSSREFS
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Cf. A120806.
Sequence in context: A024606 A074628 A031194 this_sequence A007921 A092409 A124095
Adjacent sequences: A121055 A121056 A121057 this_sequence A121059 A121060 A121061
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KEYWORD
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nonn
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AUTHOR
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Walter Kehowski (wkehowski(AT)cox.net), Aug 09 2006
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