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A161203 n-th square plus n-th squarefree number. 1
2, 6, 12, 21, 31, 43, 59, 75, 94, 114, 136, 161, 188, 217, 247, 279, 315, 353, 391, 431, 474, 518, 564, 613, 663, 715, 770, 826, 884, 946, 1008, 1075, 1142, 1211, 1282, 1354, 1428, 1505, 1583 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The subsequence of primes begins: 2, 31, 43, 59, 353, 431, 613, 1583. What primes occur in the sequence?

LINKS

Table of n, a(n) for n=1..39.

FORMULA

a(n) = n^2 + A005117(n) = A000290(n) + A005117(n).

EXAMPLE

a(1) = 1^2 + 1.

a(2) = 2^2 + 2.

a(3) = 3^2 + 3.

a(4) = 4^2 + 5.

MATHEMATICA

Module[{nn=40, sqs, sfree}, sqs=Range[nn]^2; sfree=Take[Select[Range[3nn], SquareFreeQ], nn]; Total/@Thread[{sqs, sfree}]] (* Harvey P. Dale, May 06 2012 *)

CROSSREFS

Cf. A000290, A005117.

Sequence in context: A106372 A214916 A323291 * A292768 A184637 A022450

Adjacent sequences:  A161200 A161201 A161202 * A161204 A161205 A161206

KEYWORD

nonn,easy

AUTHOR

Jonathan Vos Post, Jan 20 2011

EXTENSIONS

Corrected (75 inserted) by Harvey P. Dale, May 06 2012

STATUS

approved

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Last modified March 18 17:51 EDT 2019. Contains 321292 sequences. (Running on oeis4.)