A336864 - OEIS

%I #42 Aug 17 2020 22:24:18

%S 0,24,2510,5210,8991,56384,348732,460719,867839,28997919,193889375,

%T 254181375,419321664,1018179999,2654951424,1297015971839,

%U 62061633644031

%N Bogotá numbers k such that k + 1 is also Bogotá number.

%C a(18) > 10^15 if it exists. - _David A. Corneth_, Aug 06 2020

%C From _Chai Wah Wu_, Aug 17 2020: (Start)

%C The following numbers are terms:

%C 2805402158142975 = 153931531311*(1*5*3*9*3*1*5*3*1*3*1*1) = 111822471227*(1*1*1*8*2*2*4*7*1*2*2*7) - 1.

%C 8748948067725824 = 2441112742111*(2*4*4*1*1*1*2*7*4*2*1*1*1) = 53339113353*(5*3*3*3*9*1*1*3*3*5*3) - 1.

%C (End)

%H Puzzling Stackexchange, <a href="https://puzzling.stackexchange.com/questions/98998/pairs-of-bogot%c3%a1-numbers?noredirect=1#comment281441_98998">Pairs of Bogotá numbers</a>, 2020.

%e    n | a(n)                               a(n)+1

%e -----+------------------------------------------------------------------

%e    1 | 0 = 0 * 0                          1 = 1 * 1

%e    2 | 24 = 12 * (1*2)                    25 = 5 * 5

%e    3 | 2510 = 251 * (2*5*1)               2511 = 93 * (9*3)

%e    4 | 5210 = 521 * (5*2*1)               5211 = 193 * (1*9*3)

%e    5 | 8991 = 333 * (3*3*3)               8992 = 1124 * (1*1*2*4)

%e    6 | 56384 = 881 * (8*8*1)              56385 = 537 * (5*3*7)

%e    7 | 348732 = 3229 * (3*2*2*9)          348733 = 7117 * (7*1*1*7)

%e    8 | 460719 = 7313 * (7*3*1*3)          460720 = 11518 * (1*1*5*1*8)

%e    9 | 867839 = 17711 * (1*7*7*1*1)       867840 = 5424 * (5*4*2*4)

%e   10 | 28997919 = 119333 * (1*1*9*3*3*3)  28997920 = 51782 * (5*1*7*8*2)

%Y Cf. A336826.

%K nonn,more,base

%O 1,2

%A _Seiichi Manyama_, Aug 06 2020

%E a(11)-a(17) from _David A. Corneth_, Aug 06 2020