A048362
a(n) is the index of the smallest triangular number containing exactly n 7's.
Original entry on oeis.org
12, 59, 381, 3684, 8692, 70381, 122292, 3762381, 7453707, 18856074, 124721736, 587838545, 3996943276, 18845571218, 27483805332, 394393554074, 1246890354231, 11642661866667, 88292437929618, 184774336842416, 1158255177391940, 5962836170393707, 37870196138329618, 59623111421253050, 107479087154457892
Offset: 1
Cf.
A036524,
A048352,
A048355,
A048356,
A048357,
A048358,
A048359,
A048360,
A048361,
A048363,
A048364,
A048543.
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nsmall = Table[Infinity, 20];
For[i = 0, i <= 10^6, i++, p = PolygonalNumber[i];
n0 = Count[IntegerDigits[p], 7];
If[nsmall[[n0]] > i, nsmall[[n0]] = i]];
ReplaceAll[nsmall, Infinity -> "?"] (* Robert Price, Mar 22 2020 *)
A036534
Smallest cube containing exactly n 7's.
Original entry on oeis.org
0, 27, 17576, 571787, 5177717, 7797729087, 25750777177, 7707245470777, 744736797077707, 17373777757776999, 77777383297757779, 77077787864771842777, 2717772770751727979277, 74677779777959671778577, 787773477172377877676776, 77227778717777797207914717
Offset: 0
-
nsmall = Table[Infinity, 20];
For[i = 0, i <= 10^6, i++, n0 = Count[IntegerDigits[i^3], 7];
If[nsmall[[n0 + 1]] > i^3, nsmall[[n0 + 1]] = i^3]];
Cases[nsmall, ?NumberQ] (* _Robert Price, Mar 21 2020 *)
A036514
Smallest square containing exactly n 7's.
Original entry on oeis.org
576, 5776, 179776, 12787776, 77774761, 7907477776, 77770707876, 4477777637776, 77777477275716, 3777771174707776, 76978737777779776, 276767777777770756, 3777077879777771776, 477772772701777877776, 39877777877357777777476, 67777770773777677177744
Offset: 1
-
a[n_] := Block[{k=1}, While[DigitCount[k^2, 10, 7] != n, k++]; k]; Array[a, 6] (* Giovanni Resta, Jul 27 2018 *)
Showing 1-3 of 3 results.
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