[seqfan] Re: Rif: Re: Insert "+" and always get a prime

[Robert G. Wilson v]

%I A000001
%N A000001 Magnanimous Numbers
%S A000001 11, 12, 14, 16, 20, 21, 23, 25, 29, 30, 32, 34, 38, 41, 43, 47, 49, 50, 52, 56, 58, 61, 65, 67, 70, 74, 76, 83, 85, 89, 92, 94, 98, 101, 110, 112, 116, 118, 130, 136, 152, 158, 170, 172, 203, 209, 221, 227, 229, 245, 265, 281, 310, 316, 334, 338, 356, 358, 370, 376, 394, 398, 401, 403, 407, 425, 443, 449, 467, 485,
%O A000001 1,1
%C A000001 A number such that the sum obtained inserting a + among its digit in any position gives a prime.
%H A000001 Giovanni Resta, <a href="http://www.numbersaplenty.com/set/magnanimous_number/more.php"> Numbers Aplenty</a>
%e A000001 5992 is in the sequence since 599+2 = 601 and 59+92 =  and 5+992 = 997 and each and evey one is a prime.
%t A000001 fQ[n_] := Block[{idn = IntegerDigits@ n, lng = Floor@ Log10@ n + 1}, Union@ PrimeQ@ Table[ FromDigits[ Take[ idn, i]] + FromDigits[ Take[ idn, -lng + i]], {i, lng - 1}] == {True}]; Select[ Range@ 500, fQ]
%Y A000001
%K A000001 easy
%A A000001 Giovanni Resta, Dec 25 2014

-----Original Message-----
From: SeqFan [mailto:seqfan-bounces at list.seqfan.eu] On Behalf Of Hans Havermann
Sent: Wednesday, December 24, 2014 2:02 PM
To: Sequence Fanatics Discussion list
Subject: [seqfan] Re: Rif: Re: Insert "+" and always get a prime

David Wilson:

> I take it that internal zeroes are not allowed, e.g. 400044049 doesn't pass muster?

I've just discovered that allowing the internal zeros probably makes for a better sequence and that Giovanni Resta already charted them (under the name "magnanimous"):

http://www.numbersaplenty.com/set/magnanimous_number/

Giovanni, you did not include 20, 101, 1001. Presumably no others.

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