A177678 - OEIS

%I #8 May 08 2021 02:22:25

%S 353,373,727,757,11311,31013,31513,33533,37273,37573,39293,71317,

%T 71917,77977,1175711,1178711,1317131,1513151,1917191,3103013,3106013,

%U 3127213,3135313,3155513,3160613,3166613,3181813,3193913,3198913,3304033

%N Palindromic primes p = q//r//q such that q and r are also palindromic primes.

%C p = palprime(i), q = palprime(j), r = palprime(k) (see A002385).

%C Indices (i,j,k): (12,2,3), (13,2,4), (15,4,1), (16,4,3), (24,5,2), (52,2,6), (53,2,8), (56,2,12), (65,2,15), (66,2,16), (70,2,20), (74,4,7), (75,4,10), (88,4,18), (140,11,16), (142,11,17), (174,7,4), (206,8,2), (282,10,4), (318,2,21), (319,2,23), (320,2,27), (321,11,3), (323,2,35), (325,2,36), (326,2,39), (327,2,42), (329,2,44), (331,2,45), (354,2,49), (356,2,50), (357,2,52), (358,2,53), (365,2,61), (366,2,63), (368,2,64), (370,2,67), (372,2,70), (424,2,76), (426,2,79), (430,2,84), (434,2,86), (435,2,87), (437,2,89), (439,2,92), (440,2,94), (464,2,97), (467,2,102), (468,2,103), (469,2,107).

%C Note an example that the description with q and r is not (necessarily) unique: (2388,2,179) or (2388,11,14) for 313383313 = 3//1338331//3 = 313//383//313.

%D M. Gardner: Mathematischer Zirkus, Ullstein Berlin-Frankfurt/Main-Wien, 1988

%D K. G. Kroeber: Ein Esel lese nie. Mathematik der Palindrome, Rowohlt Tb., Hamburg, 2003

%e 3 = palprime(2), 5 = palprime(3), 3//5//3 = 353 = palprime(12) is first term.

%e 3 = palprime(2), 7 = palprime(4), 3//7//3 = 373 = palprime(13) is 2nd term.

%Y Cf. A002385, A176465.

%K nonn,base

%O 1,1

%A Eva-Maria Zschorn (e-m.zschorn(AT)zaschendorf.km3.de), May 10 2010