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

[Lars Blomberg]

The first 200 terms using subtraction (and disallowing those that have any difference = 0 or 1)

13,14,16,18,20,24,25,27,29,30,31,35,36,38,41,42,46,47,49,50,52,53,57,
58,61,63,64,68,69,70,72,74,75,79,81,83,85,86,92,94,96,97,114,118,130,
132,138,154,174,190,198,225,245,263,269,285,310,332,334,356,370,376,
392,421,441,447,463,465,487,518,536,552,558,623,629,643,665,667,689,
710,714,730,736,754,774,790,796,845,867,912,956,970,992,1114,1152,
1158,1332,1354,1510,1614,1758,1930,1992,1998,2241,2421,2465,2663,2685,
2729,2825,2841,2865,3154,3310,3370,3376,3392,3436,3512,3596,3634,3730,
3790,3956,3970,4245,4341,4467,4663,4665,4687,4867,5156,5514,5592,5658,
5952,5996,6163,6245,6269,6365,6563,6623,6689,6863,7134,7270,7314,7390,
7396,7570,7734,7936,8241,8265,8285,8625,8667,8669,8847,8865,8885,9290,
9356,9736,9896,9976,9992,11532,11598,11952,15154,17574,24263,24623,
26265,33190,37396,44865,46425,46485,46867,53532,53936,59936,62663,
62669,66665,66667,68669,71958,73534,73930,79158,91330,93370,93932,
93976

/Lars

-----Ursprungligt meddelande-----
Från: SeqFan [mailto:seqfan-bounces at list.seqfan.eu] För john.mason at lispa.it
Skickat: den 22 december 2014 19:46
Till: Sequence Fanatics Discussion list
Ämne: [seqfan] Re: Insert "+" and always get a prime


I suppose you could do the same with the minus sign, but meaning absolute difference, rather than simple subtraction.
So 13 and many other 2-digit numbers would be included, and 114 as the first (I think) 3-digit number.
John

Inviato da iPad

> Il giorno 22 Dec 2014, alle ore 15:47, "Eric Angelini"
<Eric.Angelini at kntv.be> ha scritto:
>
> Hello SeqFans,
> Look at those integers:
>
> 110,112,116,118,130,136
>
> You will always get a prime if you insert a "+" sign inside them, no 
> matter where:
>
> 110 --> 1+10=11 and 11+0=11
> 112 --> 1+12=13 and 11+2=13
> 116 --> 17
> 118 --> 19
> 130 --> 1+30=31 and 13+0=13
> 136 --> 1+36=37 and 13+6=19
>
> 101 is not an integer with this property as 1+01=2 is not allowed (no 
> substring starting with "0").
>
> I guess S, the sequence of integers that share this property) will 
> start like this:
>
> S = 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, 110, 112, 116, 118, 130, 136,...
> Best,
> É.
>
>
>
>
>
>
>
>
>
> _______________________________________________
>
> Seqfan Mailing list - http://list.seqfan.eu/


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