[seqfan] Re: I wonder

Robert G. Wilson v rgwv at rgwv.com
Sun Jul 18 07:32:29 CEST 2010

```Et al,

Using Mathematica:
f[n_] := n^2/PrimePi at n; s = Select[Range[2, 1000], IntegerQ at f@# &]; f at s

s={2, 4, 6, 8, 10, 20, 24, 27, 30, 33, 56, 66, 96, 100, 120, 136, 156, 230,
252, 312, 330, 335, 340, 350, 355, 360, 504, 528, 594, 616, 660, 671, 700,
720, 765, 828, 870, 954}

f at s = {4, 8, 12, 16, 25, 50, 64, 81, 90, 99, 196, 242, 384, 400, 480, 578,
676, 1058, 1176, 1521, 1650, 1675, 1700, 1750, 1775, 1800, 2646, 2816, 3267,
3388, 3630, 3721, 3920, 4050, 4335, 4761, 5046, 5618}

Sincerely yours, Bob.
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From: "Veikko Pohjola" <veikko at nordem.fi>
Sent: Saturday, July 17, 2010 3:18 AM
To: "Sequence Fanatics Discussion list" <seqfan at list.seqfan.eu>
Subject: [seqfan]  I wonder

> Might these be of some more general interest?
> 1. The sequence a(i) of the integer terms of a(n) = n^2/PrimePi(n),
> n=2,3,4,....
> a(i) = 4, 8, 12, 16, 25, 50, 64, 81, 90, 99, 196, 242, 384, 400, ...
> 2. The sequence n(i) of the integer terms of a(n)
> n(i) = 2, 4, 6, 8, 10, 20, 24, 27, 30, 33, 56, 66, 96, 100, ...
>
> For me, so far, they just look nicely progressing sequences.
> Veikko
>
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>

```