A034817
Concatenations C1 and C2 and C3 are all prime (see the comment lines).
Original entry on oeis.org
63, 333, 621, 3339, 4557, 8127, 13977, 16827, 18177, 21921, 27393, 34989, 40023, 40047, 46917, 59727, 61203, 79467, 94767, 95079, 100821, 102771, 104859, 106527, 113883, 114123, 143433, 147123, 156201, 158409, 160149, 196737, 209277, 209961
Offset: 0
n=95079 -> previous prime is 95071, next prime is 95083, thus '9501795079' and '9507995083' and '950719507995083' are all three primes.
A034818
Concatenations C1 and C2 and C3 are all prime (see the comment lines).
Original entry on oeis.org
657, 4929, 10647, 18291, 20907, 22653, 27381, 28053, 28671, 42471, 48441, 57363, 69651, 79569, 89853, 93261, 95967, 101283, 110763, 119481, 128613, 145719, 149409, 174993, 201417, 204861, 205329, 221883, 248391, 269199, 272799, 293451
Offset: 0
n=95967 -> next prime is 95971, previous prime is 95959, thus '9597195967' and '9596795959' and '959719596795959' are all three primes.
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ccatQ[n_]:=Module[{idn=IntegerDigits[n],pp=IntegerDigits[NextPrime[n,-1]], np= IntegerDigits[ NextPrime[n]]}, And@@PrimeQ[{FromDigits[ Join[np, idn]], FromDigits[Join[idn,pp]],FromDigits[Join[np,idn,pp]]}]]; Select[ Range[300000],ccatQ] (* Harvey P. Dale, Sep 09 2011 *)
A034819
Concatenations C1 and C2 and C3 and C4 are all prime (see the comment lines).
Original entry on oeis.org
51, 63, 123, 597, 687, 987, 4429, 12237, 18291, 20013, 29953, 31863, 34653, 48023, 52703, 57147, 59337, 62097, 66727, 71733, 81263, 86589, 101211, 105501, 118617, 121397, 134013, 146191, 147151, 155937, 174723, 175797, 179191, 180189, 205287
Offset: 0
n=105501 -> next prime is 105503, previous prime is 105499, thus '105503105501' and '105501105503' and '105501105499' and '105499105501' are all four primes.
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