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A045798
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Oddish numbers (prime to 10 and 10's digit is odd).
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15
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11, 13, 17, 19, 31, 33, 37, 39, 51, 53, 57, 59, 71, 73, 77, 79, 91, 93, 97, 99, 111, 113, 117, 119, 131, 133, 137, 139, 151, 153, 157, 159, 171, 173, 177, 179, 191, 193, 197, 199, 211, 213, 217, 219, 231, 233, 237, 239, 251, 253, 257, 259
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,1
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COMMENTS
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Numbers congruent to {11, 13, 17, 19} mod 20.
Numbers k such that Kronecker(-20,k) = A289741(k) = -1. (End)
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LINKS
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FORMULA
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Conjecture a(n) = a(n-1)+a(n-4)-a(n-5). G.f.: x*(11+2*x+4*x^2+2*x^3+x^4)/((1-x)^2*(1+x)*(1+x^2)). - Colin Barker, Apr 14 2012
a(n+4) = a(n) + 20. This confirms Barker's conjecture. - Robert Israel, Mar 27 2017
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MAPLE
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seq(seq(20*j + k, k = [11, 13, 17, 19]), j=0..100); # Robert Israel, Mar 27 2017
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MATHEMATICA
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Table[10n+{1, 3, 7, 9}, {n, 1, 31, 2}]//Flatten (* Harvey P. Dale, Oct 01 2019 *)
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PROG
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(Haskell)
a045798 n = a045798_list !! (n-1)
a045798_list = filter (odd . (`mod` 10) . (`div` 10)) a045572_list
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CROSSREFS
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KEYWORD
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nonn,base,easy,nice
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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