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A045798 Oddish numbers (prime to 10 and 10's digit is odd). 15
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)
OFFSET

1,1

COMMENTS

From Jianing Song, Apr 27 2019: (Start)

Numbers congruent to {11, 13, 17, 19} mod 20.

Numbers k such that Kronecker(-20,k) = A289741(k) = -1. (End)

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

FORMULA

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) = 5n + O(1). - Charles R Greathouse IV, Feb 07 2017

a(n+4) = a(n) + 20. This confirms Barker's conjecture. - Robert Israel, Mar 27 2017

MAPLE

seq(seq(20*j + k, k = [11, 13, 17, 19]), j=0..100); # Robert Israel, Mar 27 2017

MATHEMATICA

Table[10n+{1, 3, 7, 9}, {n, 1, 31, 2}]//Flatten (* Harvey P. Dale, Oct 01 2019 *)

PROG

(Haskell)

a045798 n = a045798_list !! (n-1)

a045798_list = filter (odd . (`mod` 10) . (`div` 10)) a045572_list

-- Reinhard Zumkeller, Dec 10 2011

(PARI) is(n)=gcd(n, 10)==1 && n\10%2 \\ Charles R Greathouse IV, Feb 07 2017

CROSSREFS

Complement of A045797 with respect to A045572.

Sequence in context: A038926 A168446 A275467 * A267277 A155071 A003626

Adjacent sequences:  A045795 A045796 A045797 * A045799 A045800 A045801

KEYWORD

nonn,base,easy,nice

AUTHOR

J. H. Conway.

EXTENSIONS

More terms from Erich Friedman.

STATUS

approved

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Last modified January 23 04:16 EST 2020. Contains 331168 sequences. (Running on oeis4.)