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A034022 Numbers that are primitively or imprimitively represented by x^2+xy+y^2, but not both. 3
0, 1, 3, 4, 7, 9, 12, 13, 16, 19, 21, 25, 27, 28, 31, 36, 37, 39, 43, 48, 52, 57, 61, 63, 64, 67, 73, 75, 76, 79, 81, 84, 91, 93, 97, 100, 103, 108, 109, 111, 112, 117, 121, 124, 127, 129, 133, 139, 144, 148, 151, 156, 157, 163, 171, 172, 175, 181, 183, 189, 192, 193 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

a(n) = A198772(n) for n <= 32. - Reinhard Zumkeller, Oct 30 2011

LINKS

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

PROG

(PARI) prim(f)=for(i=1, #f~, if(f[i, 1]%3!=1 && (f[i, 1]!=3 || f[i, 2]>1), return(factorback(f)==0))); 1

imprim(f)=my(t); for(i=1, #f~, if(f[i, 1]%3<2 && f[i, 2]>1, t=1); if(f[i, 1]%3==2, if(f[i, 2]%2, return(0), t=1))); t

is(n)=my(f=factor(n)); prim(f)+imprim(f)==1 \\ Charles R Greathouse IV, Nov 04 2015

CROSSREFS

Cf. A003136, A045611, A045897.

Sequence in context: A003136 A326421 A329963 * A198772 A185256 A070992

Adjacent sequences:  A034019 A034020 A034021 * A034023 A034024 A034025

KEYWORD

nonn

AUTHOR

N. J. A. Sloane.

EXTENSIONS

Extended by Ray Chandler, Jan 29 2009

STATUS

approved

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Last modified June 25 06:20 EDT 2021. Contains 345452 sequences. (Running on oeis4.)