This error, which took me a long time to find, demonstrates the importance of useful variable names.

Using the Wolfram Language:

pp = {};
For[i = 0, i <= Max[p], i++, If[Count[p, i] != 0, pp = Join[pp, {{i, Count[pp, i]}}], -1]];
pp

Outputs:

{{1, 0}, {2, 0}, {3, 0}, {4, 0}, {5, 0}, {6, 0}, {7, 0}, {8, 0}, {9, 0}, {10, 0}, {11, 0}, {12, 0}, {13, 0}, {14, 0}, {15, 0}, {16, 0}, {17, 0}, {18, 0}, {19, 0}, {20, 0}, {21, 0}, {22, 0}, {23, 0}, {24, 0}, {25, 0}, {26, 0}, {27, 0}, {28, 0}, {29, 0}, {30, 0}, {31, 0}, {32, 0}, {33, 0}, {34, 0}, {35, 0}, {36, 0}, {37, 0}, {38, 0}, {39, 0}, {40, 0}, {41, 0}, {42, 0}, {43, 0}, {44, 0}, {45, 0}, {46, 0}, {47, 0}, {48, 0}, {49, 0}, {50, 0}, {51, 0}, {52, 0}, {53, 0}, {54, 0}, {55, 0}, {56, 0}, {57, 0}, {58, 0}, {59, 0}, {60, 0}, {61, 0}, {62, 0}, {63, 0}, {64, 0}, {65, 0}, {66, 0}, {67, 0}, {68, 0}, {69, 0}, {70, 0}, {71, 0}, {72, 0}, {73, 0}, {74, 0}, {75, 0}, {76, 0}, {77, 0}, {78, 0}, {79, 0}, {80, 0}, {81, 0}, {82, 0}, {83, 0}, {84, 0}, {85, 0}, {86, 0}, {87, 0}, {88, 0}, {89, 0}, {90, 0}, {91, 0}, {92, 0}, {93, 0}, {94, 0}, {95, 0}, {96, 0}, {97, 0}, {98, 0}, {99, 0}, {100, 0}, {101, 0}, {103, 0}, {104, 0}, {105, 0}, {106, 0}, {107, 0}, {108, 0}, {111, 0}, {112, 0}, {116, 0}, {118, 0}, {122, 0}, {125, 0}, {136, 0}, {137, 0}}

As opposed to the expected output, which should have no 0s as the second values in any of the tuples.

I spent a large amount of time examining the code to generate p before realizing that the bug was in this line.