__uint64_t test = 0;
for (int i=0; i<64; i++) {
if (i%2==0)
// if even, shift left
test = test << 1;
else {
// if uneven, shift left and make the first digit 1 (OR 1)
test = test << 1;
test |= 1;
}
}
printf("Resutltat %lld", test);

Always open for recommendations and more elegant solutions

for (int i = 0; i < 64; i++) {
if (i % 2) {
myNumber = myNumber << 1; // myNumber <<= 1; would be possible as well
myNumber = myNumber | 1; // myNumber |= 1; would be possible as well
}
else
{
myNumber = myNumber << 1; // myNumber <<= 1; would be possible as well
}
}
printf("myNumber: %lld\n", myNumber);[/code]

uint64_t big =0;
int iI = 0;
int insidecount =0;
for ( iI = 0; iI < 63; iI ++){
big = big << 1;
if (insidecount % 2 ==0){
big = big + 0x01;
}
insidecount++;
}
printf("Variable in Hex is %llx\n", big);
printf("Variable in Decimal is %llu\n",big);