* Pentagonal numbers are generated by the formula, Pn=n(3n−1)/2. The first ten pentagonal numbers are:
* 1, 5, 12, 22, 35, 51, 70, 92, 117, 145, ...
* It can be seen that P4 + P7 = 22 + 70 = 92 = P8. However, their difference, 70 − 22 = 48, is not pentagonal.
* Find the pair of pentagonal numbers, Pj and Pk, for which their sum and difference are pentagonal and D = |Pk − Pj| is minimised; what is the value of D?
*
* @author ddaniel27
*/
functionproblem44(k){
if(k<1){
thrownewError('Invalid Input')
}
while(true){
k++
constn=k*(3*k-1)/2// calculate Pk
for(letj=k-1;j>0;j--){
constm=j*(3*j-1)/2// calculate all Pj < Pk
if(isPentagonal(n-m)&&isPentagonal(n+m)){// Check sum and difference
returnn-m// return D
}
}
}
}
/**
* Function to check if a number is pentagonal or not